[Jealous idiot]

My boyfriend and I have been going together for 2 yrs now. But we did not start on the right path as he was already with someone else for 3 months or less.. Before we started going out while he was with her, he was already cheating on her with a colleague at work. Then I started working there and he started cheating on her with me(so I also have this fear of him cheating on me at work). After sometime when I accepted to have a relationship with him he broke up with her. At first it took him time and me to tell him that some of his actions were not acceptable if he wAnted to continue this relationship and that was it he changed everything for me. Apart for this one time were he was drunk and changed his msn password and spoke to his friend the one he cheated on his ex with, before me. He spoke to her about us and about me wanting things my way. ( bdw shaming me at work as I work at the same place and she told others).. And he hid it all from me sending her texts thanking her or something similar I don't remember exactly but what I remember is him telling me that he told not send back late as he was meeting with me, but I caught him as she later sent him a message on fbk... Although he broke all the contact with her I still did not manage to trust him.. . Plus I never managed to forget what he used to do in the past. And it kept haunting me till I managed to push him away. Now he wants to break up. He says he stills loves and doesn't want anyone else but after 2 yrs putting up with my issues he now needs to think for himself. And things such as he likes to joke with everyone, but off course because of my insecurites I was an idiot and did not even want him to speak to another woman. Now he started joking with other women and did not even tell me because he was fed up and to him it was nothing wrong as he did it with everyone and he knows when to stop ( that is the most difficult part for me, as I know what jokes leads to as it was what lead to our relationship) I want to change, I really do but he want believe me and he's really stubborn :/... I do not want to loose him but I was so locked up in myself fearing that he would hurt me and somebody else would take him away from me that I never noticed how sad he really was. I really feel bad and I want to make things better. I love him and he loves me. I really do no want to loose this guy, I remember when in the beginning we started going out he secretly did a test as he has a certain illness which might prevent him from having kids and when he told me that it came sort of positive meaning he would not have kids, he was really sad and crying. That was a long time ago and I think it must show he really loves me to have thought of that from the start. I 've done a lot of stupid things and the worse is that I tried to control him. Please help how can I make him see I want to change? Because he's making it quite difficult as he doesn't want to meet up. When he does it is because I have some family problems and he does not want to leave me alone..