Help?

Okay. This'll sound kind of, well, uneducated, but, I figured I'd ask anyway - I'm not even sure this is the correct board to be honest.
I had sex with a guy the day before my period. I was kind of out of it, and I didn't think to make him pull out - and he didn't.
A bit of back story: when I was 13, I was seen by a doctor who said I had a low chance of having children(due to the miscarriage of a rape baby - long story).
I'm now 17, and haven't been back to an OBGYN since. I also cannot be on birth control, because it affected my body so negatively when we tried it before for my menstrual pain.
How concerned should I be about being pregnant, taking into account it was the day before my period(I started when I woke up), and the previous doctor telling me I couldn't have children.
Help? Please?
Thanks!