20 year old- wedding in 3 weeks

I'm 20 years old. My parents never talked about sex. I've been having sex with my fiancé for over a year now. We don't use condoms because I hate the smell. I can't take birth control because my blood clotting disorder. The other day he accidentally came inside me but I started my period and everything was ok. Now I know I really like when he comes inside me. Is there anything I can do to prevent pregnancy?