What Causes Spotting With Bloating Of Abdomen?

Hi i am 19 years old just had my period 10/9/10 on a friday and just got done 10/10/10. on the 10/11/10 i had verly any blood and on 10/12/10 there was even less blood verly anything. This was to short to be a period. Two three weeks before my boyfriend rubbed the head of the penis on the vagina can there still be a chance of pregnancy. I am crabbing certain foods and my stomach feels and looks different there is a slight enlargement. Could it be im pregnant?I just had sex 10/12/10 unprotected sex. is there a possibility i might be pregnant?