I Feel I Been Trapped Into Being A Father!?

Well long story short me and a girl were highly intoxicated and we had sex. Poor decision I know. And I felt very pushed into it. 2 weeks later she says shes pregnant. Not sure if thats even possible. I find out she already has 4 kids and is still married. I told her it was a poor decision for both of us and that either she should get an abortion or put it up for adoption. I am not able to financially support a child right now and can't be a good father to this child and that I want to have a kid with someone I am married 2 and raise a kid the right way and not like this. I asked her if she was on birth control and she said yes and that the day we had sex she forgot to take her pill that day so she doubled up the next day. Not a very bright girl if she is to do something like that, there is a morning after pill you could take as well. I haven't a clue who shes been with previous to me and know very little about her. Yes I know shame on me, but everyone makes mistakes. She strung me along for several months saying she was going to get an abortion but when the day came to go and do it, she wouldn't show up. She told me she understands I am not ready to be a father and that I am not financially stable for a child right now and that I will never hear from her again and if I change my mind to give her a call. Few weeks ago I got served court papers her claiming the baby is mine, I am now scheduled to take a DNA test and I pray that its not mine. She wants full custody and child support. Clearly all she want's is money, which I have very little of and my job is not looking very promising. I don't understand why she is doing this to me and why she would lead me on like she did, lie to me about being divorced, and then come after me. I am now spending thousands that I dont have on lawyer fees and DNA testing etc. I feel as if someone has just taken all my dreams in life and shattered them. I have been very depressed over this for months now, and can't believe there is people out there like this. I am afraid to hear some of the answers, but I would like your opinion on this matter, and I am sure you people will say dont have sex then, yes I know, this was very uncharatierstic of me to do, and I dont believe a child should have been conceived like this.