Idk if I'm pregnant

I had sex with my bf last month an I never got my pd this month I still haven't gotten still... I am not throwing up or anything but I have been tired lately an have like huge appetite I don't think that's anything new. Am I pregnant or is just cause I had sex?? When should I start showing if I am what other symptoms are there I should be looking out for that I'm probably not thinking of please help me