Is pregnancy in a very short term relationship.....?

an appropriate reason to start a long term committed relationship. I made a mistake. I had been seeing this woman for roughly a total of 60 days which amounted to six different dates. Long story short she turned up pregnant. Now she says it is mine and I am not a stupid person, I know that the baby is as likely or more mine than anyone else's but still have a lingering doubt as there was a three week period where we were seperate with no intention of continuing our relationship. My primary problem is that once I knew about it she essentially refused to talk about it rationally. She wanted to act as if this is something that we planned together rather than an accident, and refused to talk about it at all. Would just clam up everytime I tried to start talking about it. Thing is this makes me feel like it was planned by her, and what I wanted doesn't matter at all. I have been divorced and have custody of my two daughters. So I have more than just myself to consider in this situation. I would never choose to abandon a child, but feel that this woman will not allow me to be part of the child's life if I choose not to be with her. Which in my mind is using the child as a weapon. This is something that she has all but said to me. I feel that I am being forced into a long term relationship with someone I hardly know, which I feel is a situation that is bound to fail. Am I just being selfish, or is this the responsible thing to do. My biggest mistake and what I regret most is that I really wasn't ready yet for another longterm relationship, and I started something with this woman. Thoughts please, and only serious comments if you don't mind. I am not putting this on here to be berated.