Cheating..need help please?

Im asking this because I know the answers will help me be more strong with my issue. My boyfriend of 4 yrs has lied to me and cheated before, but we got through that. I do not trust him and cant stand the constant mistrusting feeling. The man was just at my house over the weekend as usual and had our great time, eating out movies shopping all that . The next day he gave me his pword to put an add on craigslist for him. after thinking do I want to look and know or not I tried the pword in his email, facebook and that led to an online dating site. I found out and read all i needed to see from him to other girls, texts , phonecalls, plus his online personal ad and flirting and sending gifts. I confronted him and told him to get F****D. Im done, no way Im gone. He will not stop texting me and trying to make me believe it is his friend that used his info and through facebook account to make a profile to catch wife cheating. but it is my bf pics and his words i read.This is the biggest bunch of bullshit IVE ever been fed, plus saying he did nothing when I saw it all with my eyes. in fb and email. I want to hate his guts, and its hard,I need all the sponsor help I can get just like an AA or drug meeting. Please tell me your oppinions of this and help me to see clearly and say strong. To get rid of the lowlife MF.... thanks