Well... for starters... im seventeen years old. About week ago I went to the hospital for strep and had to get a shot of penicillin in my butt. The same day, my boyfriend came over after not seeing each other for a long while, so we fooled around. Quite a bit. I've been off DEPO provera for about 3 months. And we didn't use a condom and he didn't pull out. We did this three times in one day... my period was supposed to come 3 days after that, and is now 4 days late. I always have regular periods and they usually always come on time. I wasn't sure if the shot for my strep could cause my period to come off. Please help.