help a little sister!!!!!

Danielle
Hey girls im 18 and have had my periods since the last time i had intercourse which was may 13th every singlemonth meaning june july and august i have had had my periods, i took a home pregnancy test and it came back negative as well as blood test and came back negative, my friends kind of scared me telling me that i could still be pregnant??? Is that true should i still be worried? Can blood test be wrong my boobs hurt but i think thats because i been squeezing them everyday for a week now! Just to check is theyre sore.. i know ridiculous right? And i wake up very nauseous sometimes Anwyays it would be really helpful if u guys could answer my questions thanks god bless