15 and pregnant

I’m 15 and i think i’m pregnant. i had sex one week ago and my nipples are really sore. I was sure that i wasn’t because i saw him finish but now i’m not so sure. I’m supposed to start my period in 8 days and before my period my boobs hurt so it could be that but it’s just the nipples that hurt now. Please tell me what y’all think i should do and if y’all think i’m pregnant.