Am I normal or just a psychopath?

Hi, my real name is John and I never thought I'd use a relationship forum to help me sort out my relationship issues. I'm going try keep this short as people don't like reading paragraph after paragraph of problems.

Okay, so when I was 17 I met my very first girlfriend that I lost my virginity to(She was not a virgin at the time, she had a few lovers), everything was going great until I cheated on her...She took be back but always seem to throw what I did in my face, this then caused arguments all time. She then started going college and sleeping around. Thing is, I was very jealous over her, sometimes she deliberately made me jealous because that's what she enjoyed the most. Anyway, During the time I was with her, I was very attached to her. I got very jealous when she spoke to one single person. Each time she broke up with me I self-harmed but not in a suicide gesture but just for the pain. I felt like the pain of self-harming made me feel a little better. Once when I told her I was self-harming, she just smiles and didn't care. I left her when I was around 20 and was single ever since. After getting over her thanks to my mate Zak who eventually got a job and introduced me to some girls he knew, it helped me get over my EX Gina. But there was one girl, Emma, who to me was nothing compared to my EX. Emma was just larger than her and not as attractive. The first night I met Emma was on a house party -- we kissed because we were drunk. I never thought much of her. A few weeks went on after that night and Emma was having a house party, she said to my mate Zak to see if I wanted come this house party of hers. When I went I wanted to sleep with her because I was drunk, she refused, another month later we slept with one another.

Me and Emma were sleeping together for over a year but nothing as boyfriend and girlfriend just as mates. But just a few weeks ago, I think it was around May 23 2012, I asked her out because during the time I was sleeping with her, I told my mate Zak that I was beginning to have strong emotions/feelings for her. Now that I'm going out with her I knew I made the right choice. I love her to bits and she said that she felt these strong feelings for me too, but was upset a little how I wouldn't ask her out sooner because I was still a little confused and scared about my past relationship. So this is where things got upside-down, About 2 weeks ago or maybe more, I asked Zak if Emma ever had sex with someone else while I started sleeping with her, Zak said yes. Without saying anything, I got really angry but kept it in until me and Emma were alone. When I got her alone I shouted "Did you F**ing sleep with someone while I was having sex with you" I punched a hole in my wall, cut my hand and kicked my computer chair and had a massive bruise and lump while crying because I was upset, she was trying as well. She said yeah but after a couple of months of me meeting her and it was a one night thing because this lad she worked with was leaving and she binned her off. After She explained and I calmed down, I accepted the fact what she did and that it wasn't during our relationship and it also wasn't fair that I played her on for so long. So, couple weeks later I've noticed I'm more attached than ever. I keep getting paranoid, sad and violent. For example, last week my mate Zak had another house party, there was a few people there but one lad in particular, Zack, not to be confused with Zak was talking to Emma. Zack is a okay guy, and he knew Emma long before I knew her but somehow I always thought there was history. I think I asked Emma before and he said me and Zack never did anything. Anyway, All night I was watching like a hawk while getting violent images in my head of stabbing him or cracking a wine bottle across his head, just beating him to death. Now this is worrying because each time I see Emma talking to someone I just keep getting an image of me stabbing them several times. Sometimes these images pop up when Zak is talking with Emma, and Zak is my best mate. I can trust him and her a million percent. I love her to bits and I don't want lose her. She knows I get jealous but that doesn't stop me from letting her do what she wants. She goes work, clubs, pubs and tha. She even said herself that she gets jealous,too. And one thing that she said that kinda gave me a piece of mind is when she said "I'd have a guilty conscious if I cheated on you, babe" That made me feel better. But with these violent images, I'm afraid that these images will lead me to do something and I will lose her forever...

What should I do? please ask me questions or give me answers :) Sorry for spelling mistake and anything else

Oh, I also get sexual images of her and other lads which leads me to get angry. I try my best to control them so I don't let it out on anyone including her. it's difficult.

Op: Did you kill cats when you were little?

I know you won't listen but if you love Emma and more importantly, if you love yourself you will go to your doctor and you will as for a referral to a therapist wherein you should tell him everythng you just told here and then he will discuss with you ways to get past your "isms."
I couldn't begin to tell you the mental exercises you will need to do to find your zen.
Good luck.

P.S. If you don't want to lose her then I suggest, if nothing eles, you go to anger management classes to get a better perspective on things.