If my period ended august 13th and my boyfriend didn't pull out the 25th and my period started today could i still be pregnant ?

Pregnancy ?: "Periods" vary in length, but if your cycles are 26-30 days apart, it is unlikely given the facts provided that pregnancy did occur since ovulation would have occurred earlier than the "25th". If your period is of normal length, with usual symptoms you are probably not. If other symptoms or if normal bleeding are shorter than usual, obtain a serum (HCG) test.