I'm 18 and I wasn't sexually active for a few months & I was due for my depo shot in June but decided not to go back for it because I was so busy with getting stuff ready for school. I just had unprotected sex early morning 1am sept 15 (it's sept 17). When I woke up that morning my nipples were so sore. Today my nipples look like they have red patches & my nipples get hard like a rock & hurt to touch them. I don't think I can be pregnant because I haven't gotten my period since I've been off the shot & it's been 3 months. Can it be something else?