Should i stick around to love my pregnant girl friend who slept with another man?

I met this girl out of nowhere and I thought she was perfect. When we met I had just gotten out of a relatinship about a month prior and she had also just left her husband of about 3 years togeather for 5. With so many things in common I didnt think i could find anyone else to fit my puzzle so she moved in after only about a month. She has plenty of family here, she had other places to go but we were in puppy love and it felt so good for both of us. Things were good for a while, it was summer time and I ahve never really had a serious girl friend and I like to go out party, drink heavly and have fun. Well after time goes on I drink more and more to a point where she had asked e to stop...I didnt stop. I stayed at a girlfriends house after an argument with her and a long night at work. All hell broke loose. I didnt cheat. However she didnt believe me and the arugument went on and on and still goes on to this day: because I didnt call. Shortly after maybe 3 weeks I did it again but this time I stayed at a buddys house and the friend who I stayed with the first time was there with us. It was also made into a big deal and maybe it is to most women but to me its jsut not a big deal. Im alive, im not doing anything i shouldnt be doing so just let it be... It was a back breaker for me because I havnt had a serious relationship and i didnt want to be told what to do or when to do it. She moved out after a lot of drunk excurisions with and with out me. She didnt want to leave she says but i see why she had to go. I told her to leave for one and I would say mean things when I got drunk. "why are you here?" "I dont love you" "Nothing you say matters to me" things like this are unacceptible and I know that now after being sober for 5 months. For me it was a wall because she was getting under my skin. I love this woman and I am sorry for what I have done. Soon after she moved out we contacted each other and are still in touch because she is pregnate. She moved on to several men only to have with one guy she says and a few dates. What she tells me is completly unbelievable to me because the time line dosnt match up and she did have an affair to leave her husband, she is very capable of lying and cheating. We went on a vacation to the mountains and had a good time with some too. But before we left I asked her if she had been ual with anyone she said no but she had been hanging out with a guy. Me being in love didnt care I can move on from that. Well low and behold the past 5 months she has lied to me and she did have with a guy probally more than once like she says but I dont know what to believe. During this whole time I have been sober, I have bent over backwards to see and talk to her any time i could. She would blow me off to go out drinking with people she wouldnt mention names but i can imagine this guy or guys she would meet out. The day we find out she is pregnate she decides to tell me this. Its only been a month I am worried its not my kid and also just the trust issue. I love her always will in a way but Im not sure if I should stick around to love her anymore. If she would ahve told me 5 months ago she was sleeping with a nother man I would have left however she played me and she was having with me the whole time too. Im pissed off. We were not technicaly togeather but I think she went to far. If anyone has ever been in this kind of situation please give me a word or two of advise please...