Pregnant ? please help ?

im pretty young and i have recently been having stomach cramps and just noticed my nipples looking bigger as well as more prominent veins by my nipples. im scared and nervous that i may be pregnant. my boyfriend and I do use condoms during sex but there's a possibility that something may have happened when we were just fooling around. Im expecting my period in about a week so ill know for sure then but from the sounds of it what are my chances are of being pregnant?