had sex for the first time and now paranoid i may be pregnan

I know this is going to sound wierd but i had sex for the first time in october and havnt had sex since, i have taken pregnancy tests that are negative and my period has come but i have heard people say that tests can be wrong and you can still have blood discharge while pregnant. I am just worried becuase i seem to have a bulge in my lower stomach area and i do not know if it is just from bloating or i am just going insane over the fact of being pregnant. can someone please help i would really like to have some closure on this subject so i can stop being stressed and focus on my school work