Lost for words

So a just a bit of back ground. Me and my ex partner tried for a baby for nearly 4 years after suffering a miscarriage when we first got together. We had countless tests and apparently I had pcos and would struggle to get pregnant.. come further down the line I left my cheating ex partner and stayed single for a couple of month lost quite a bit of weight due to stress and I ended up having a one night stand with someone and would you believe it I got pregnant. Alls it took was that once. Not that I was planning it I was wasted and didn't even think about protection. Now I'm between two minds of what to do I don't know the man I slept with didn't get his name number or nothing. So if I was to go forward and have this baby I would be bringing that mans child into the world and he wouldn't have a clue. Just wondering what others would do in my situation