I NEED ADVICE PLEASE READ AM I PREGNANT?

I USUALLY HAVE IRREGULAR PERIODS...LIKE ONE EVERY THREE MONTHS THE DOCTOR SAID THAT EVERYTHING WAS FINE. BUT NOW I'M HAVING SEX AND I CAN'T TELL IF I'M PREGNANT OR IF ITS JUST THE IRREGULAR PERIOD? I'M ALSO ON HIGH BLOOD PRESSURE MEDICATION AND THAT MAKES ME SLEEPY AND TIRED BUT THATS ALSO A SYMPTOM OF PREGNANCY, I FEEL BLOATED ALL THE TIME, I CRAVING FOOD MORE THAN USUAL AND I HAVE PAIN IN MY PELVIC AREA. ALTHOUGH I DO NOT HAVE NAUSEA. I HAVE TAKEN SEVERAL PREGNANCY TEST AND THE WERE ALL NEGATIVE.
CAN SOME COMMET AND GIVE ME SOME INSIGHT ON WHAT I SHOULD? VERY CONFUSED %-) I'M 18 YEARS OLD