Hi Sami!!!
I am glad things are getting better. I know what you mean by the last chance that is not one. Unfortunately, they do abuse of that a lot some of them!!!! And i am one of those girls who give 100 last chances.
I do not know if that will help you a bit but I know some men fantasize a lot. My b/f just fantasizes on almost every women he sees, on tv, friends of mine..... I felt very insecure at first but got used to it now. I do not think he will physically cheat on me but he has a very active mind and me not being slim or a supermodel makes him want better looking ones! But he also knows what he has got to lose if he does anything!!! Your b/f is only 20 and has a lot of growing up to do!!! Mine is 28 and he still has a fair bit to do lol My brother only became very mature at 32!!!!
I am not finding them excuses but I found out that when i was getting upset about him chatting to his ex on the net and sending her flirty messages, it did make it worse, he would write to her sometimes 12 times in the day. One day, i totally stopped nagging him even though sometimes i am tempted and he stopped, seeing he did not caught my attention anymore. He still has got his private mail box but i'd rather not try to look at it, he knows he is going to be a daddy and not being married i can refuse him every single rights if he did anything silly, not that i think he wants to. But i still have nightmares of his ex coming back to him as it nearly happened in the first 3 months of our relationship, she tried to have sex with him just to show me she could have him anytime but he told me he told her to go away, although very tempted because he considered her as the love of his life and she is soooooo great!!! I believe he did not because he is a very honnest person, too honnest and he was not obliged to tell me that she tried it on, he could have hidden it.
funny enough, he never talked about her now, but i still have hidden fears somewhere, must be pregnancy lol
Anyway, glad it is getting better for you!!!!
Nath