How to get over a sick relationship?

I have been through a a horrible relationship with constant emotional and verbal abuse, and I'm still in it... The problem is that he wasn't the first man in my life. Well, he was the second but that wasn't enough for him so he would constantly make me feel like a cheap whore because of that, saying that it is a huge guilt, my guilt in front of him, so I have to pay all my life for that and do whatever he wants so he could forgive me. Don't ask me why I didn't leave, I just couldn't, although I didn't consider myself a weak person. So he repeatedly left me, saying that he couldn't live with that and I wasn't enough for him, and then came back, or I run at him pleading for forgiveness for my “mistake”. These arguments started of nothing, the problem was that it happened not only in personal, so he made me feel like a slut in public too. I got to the point that none of my friends or his friends understood me how could I ever tolerate such thing and didn't leave him in the first place. Well, I just couldn't. He made me feel like a queen in his “good moments”, so I had just this immense fear that no one would ever love me like he did. A year and a half he repeated day by day, every day, that he is the best man in the world, and I would never ever forgive myself if I ever let him go, so I got to the point to believe it myself. Got to the point to be afraid of saying or doing something that he wouldn't like, because of his permanent blackmail that he will leave me and I'll never find someone else, live all my life alone, and regretting that I lost him.
Besides that, he is EXTREMELY possessive, I can't handle that anymore, he doesn't want me to go anywhere without him, and blames me for that, says that his possessiveness is a consequence of my past, and I am responsible for that.
The problem is that this situation is still not over... I don't know how to finish it and what to do, I feel like I'm dying without him, and I don't respect myself anymore for letting him treat me like this, if I'm with him. I just see no solution.

Fake your own death and see if he even bothers to come to the funeral.

you've gotta be brave and break the cycle. best man in the world/ gimme a break. he's insecure pathetic and an abuser. he's not worth sticking round for the occasional 'good moments'. you're NOT a whore. cut this guy outa your life he's not worth your smiles, tears or thoughts. i'd personally go find him and have a 'chat' but stuff like that''s illegal apparently.

I've been there! Here is what you need to do:

Stay with him until you are 'done'. This way you will never wonder "what if?". Totally eliminate ALL "what ifs" until the point that you are sick of it. And I mean absolutely, positively, sick of his shit (because that's what it is) and realize that with 6 billion people in the world, your person is out there. Everything happens for a reason and I promise that you will get stronger, not immediately after, but after some time. Also realize that after you leave him, you may rebound with someone (this is natural) BUT IF IT DOESN"T WORK OUT WITH YOUR REBOUND DO NOT RETURN TO YOUR EX!!!!!!!

Dating is all about finding what makes you happy and it's okay if it takes more than one person to show you that. I personally think that you are loveable and you WILL find someone who treats you right ALL THE TIME.

Isn't that something you want for yourself? Now... how bad do you want it?

Thank you all for your reply.
I know I should leave, I am conscious of that, I myself would advise anyone in my situation to do that, my mind tells me that, but I just can't do it. I don't know how to explain and what he did to me. It's like this huge panic and lack of oxygen is assaulting me every time he talks that we are breaking up.
In fact, we were broken up for more than 2 weeks, again because I didn't do what he wanted me to do, and I've been through hell. Somehow, I don't know how, I did have the power not to call him or contact him in any way, although it was extremely difficult, I wanted to die every morning I woke up, if I was able to get some sleep. With the help of my friends I somehow survived these two weeks and tried to convince myself that it's over, and I have to survive, and then he called... We saw each other, began to talk... he tells me (and had told me for a year and a half) that the fact that he was not the first man in my life bothers him so much because he loves me so much, he just can't stand this thought, and how much he is suffering... And again, he made me feel like a slut, guilty that I didn't wait for him, and now he is saying that I have to struggle for the relationship, I have to change and realize my huge guilt. Even when I do admit that ok, it is a guilt, he is still not satisfied, and says that I don't realize it and I have to feel all this pain in order not to make mistakes again.
He wants now us to get back together and me to change... and I just don't find the strength to leave him! I don't know how he implanted this fear in me that no one would ever love me as much as he does (even if it sounds ridiculous...). We had plans together, every day he says how much he loves me and whats family and children with me.
When I read people saying that I'm in fact a valuable human being, I burst into tears!!! I realized I lost most part of respect for myself...

it doesn't sound like you're getting much support from friends and family. if he's the only one in your life that even occasionally shows support of course you're gona be more dependant on him.

"YOUR GUILT"? What is this?! Did you cheat on him, or was he simply your second boyfriend? Honey, let me tell you, this is brainwashing to the max!!! Do not stand for this abuse, you don't deserve it. Don't let him tell you this garbage about how you need to suffer because he is suffering at the thought of you being with someone before him - oh please! He is only looking for someone he can control and I guarantee you, once you stick up for yourself and he sees he can't control you anymore, he will move on, but most importantly, so will you.

Let me ask you this question: what is so wonderful about him, that you can't leave? What proof do you have from all of his actions, that he actually LOVES you, more so that you will find no one that "loves" you like he does? Love is NOT manipulation, verbal abuse, emotional battery, or any other horrible thing he has done.

One day you will realize this is all wrong - enough that you will leave. Maybe it won't be today, maybe it won't be tomorrow, but it will happen. Get your support system together, family and friends. Make sure they will be there to help you through. I won't say there won't be pain in breaking up, that happens. Take one day at a time and focus on You. Take up some hobbies, keep yourself busy. It will get better with time, I promise!

Keep on building up the courage, day by day.

Be strong!