Hi, I'm glad you wrote back, especially for the other women in your situation now. It's easy to fall down a rabbit hole of obsessive thinking when you are anxious, but just because the brain can think up a whole bunch of "what if" questions it does not mean that the questions are valid. The brain is capable of thinking up a hundred false scenarios a day to be anxious about. But, as a good OCD therapist I know says, "You don't have to believe everything you think."
If your OCD is taking you to the woodshed, please work with a counselor or therapist that specializes in OCD. (Ask your doctor for a recommendation if you don't know one.) Cognitive behavioral therapy works well for OCD, and pretty fast also. And if you need a supportive medication, SSRIs like Prozac and Zoloft along with the therapy can make a huge difference in breaking the grip of OCD.
Good luck to you, I hope you write in with some reassurance occasionally to the others who write in to this site, since often it is someone who seriously doesn't have a reason to be fearful about who the dad is, but can't stop worrying anyway.