need help asap!! so much pain

so yesterday was the 3rd time i've had sex with my boyfriend. everytime we've done it, it hasn't lasted longer than 5 minutes. yesterday we did it for 30-35 minutes. when he started to do it "doggy style" it did start hurting but i thought that was normal obviously. but last night.. about 4 hours after i started to get EXTREME pain in my lower abdomen. it hurts very bad to stand or sit up straight. people are saying it's normal because ofc my body is not used to something like that being in me and i'm just sore but i need some opinions. i can't tell my mom about why i'm in this pain because i'm still a teenager... this morning the pain is a little better but still painful. he doesn't have any STDS or anything like that either.