Maybe you both had real love before, but it's pretty simple you both don't now. Emphasis on the BOTH part because you are both a part of this, regardless of how strong your feelings are.
First of all, call him out on the part about he said he didn't love you anymore. That you weren't really dating. That's pretty ****ed up. He felt that way and he can't help how he feels. To downplay what you had with him is insulting to you and disrespectful. Yet here we go with you continuing on to.....
Having sex with another guy. Drunk is never an excuse and no matter how much the guy antagonized, you are completely and utterly responsible for your decisions. You chose to have sex with the guy. You have a million reasons, but they aren't excuses. Accept that fact.
Instead of getting to the point and handling the relationship on your own (since he wasn't), you let yourself drift slowly into despair where getting with another guy seemed like a good idea. You shouldn't ever let it get to that point. You need to be up front and honest about how you feel. It's key. And do not worry about losing him and the half assed relationship you have going on now because there will always be somebody else to take his place. Not the same person, but somebody you can love just the same.
It's your first real relationship and you honestly didn't know any better. I get that. You shouldn't be seeking forgiveness, you shouldn't be trying to get back into a broken relationship that is so scarred and damaged, and you will never get anybody back by trying to get him back. You shouldn't have to wait for anyone. You need to accept on your own that it isn't worth it. You made alot of mistakes but you have to walk away with these lessons. It's important to your growth, to develop a sense of independence that you don't need anybody in your life, and to be ready for a stronger, more advanced relationship in the future. You don't need to be punished for this. You are talking about get out of jail free cards, is this how you see relationships and marriages as?
Break ups happen all the time. How we deal with it, how we bounce back, really says alot about who we are and how much character we have. You do not need him in your life, and you do not need the guilt of what you did on your conscience. As long as you know it's wrong, don't do it again. Be honest about how you feel and walk away with your head held high before you decide that sleeping with other guys is the right move.
Everything will be okay. You have to cut him out and start living life on your own again. I promise you are going to look back on this one day and laugh at the absurdity of this whole situation.
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.