I might be pregnant

Alright girls! Help me out!

I had a one night stand with this guy and he came inside of me! Yes, stupid on our part. My period is coming up maybe the next week or so. Now I'm worried, I might be pregnant. (Hopefully I'm not). But I'm just thinking if I do get pregnant and I keep the baby. Can I make him pay child support? We are not together, we are just friends.