Could I be pregnant

Okay so last month on December 27 I had sex ... I ovulated the 26th me and the boy had unprotected sex and he came in me .. long story short my breast have been feeling very tender like my nipples are hurting a tiny bit . I keep having cramps minor cramps and I felt nauseous one time and I’ve been having headaches could I be pregnant? Also I’ve been told the day after ovulation is a fertile day so I’m kinda worried