One time sex..?

I had sex with a guy and I was so off checking if I was in the "safe period" - I wasn't, I ovulated around the time we meet. He came inside me and I know this is a weird question. What's the chance that I got pregnant? I know it's possible but anyway..? I've had unprotected sex alot (with guys I know) and never got pregnant, but now somehow I worry? Please don't tell me that I am stupid. I KNOW!