I've had sex a total of four times. Twice it was unprotected the first time was in may but i got my period shortly after. the most recent time was July 29, 2013 i got my period the next day. i then had protected sex some time in August. And got my period on time. I don't have sore boobs or any other symptoms except back pain but I'm not sure if it is a result of marching band. i also took a pt before my last period and it was neg. Only thing i feel is back pain and upset stomach.. should i be worried about anything?