Possible Pregnancy? Symptoms, Timeline & What to Do

Question
Hello.  My name is Chris and I'm 23.  I keep telling myself that it is not possible that I'm pregnant but the people around me (all who have kids) try to tell me otherwise.  I keep saying I would DEFINITELY know by now.  I've only been with one man, once and that was back on around June 11th.  I got my period 2 weeks later (I'm still on the pill) and have gotten every one since (but I know that does NOT necessarily mean I'm not pregnant).  Some of my friends have had their period when they were pregnant (tho rare).  For 2 or 3 months after I had sex, I had a sharp pain in my left side, but then went away.  Since then (and during) I've been really tired, having headaches, and just feeling strange.  Lately, I've gained a little (only about 5 pounds, but I'm small so that's actually a lot for me), but it seems like more because it's all in my lower stomach (it's never been that shape before).  It feels like i'm pushing out my stomach but i'm not.  It hurts to lay on my stomach, and it's gotten a little harder.  My breasts have been sensitive lately (and that's not common for me since I had a reduction at 17).  I took 2 pregnancy tests back in August or September (but I know those are not 100% accurate).  I know it is very unlikely that I am pregnant, but I can't shake this feeling.  Is it possible that I'm pregnant?  If not, what do you think it could be?
Thanks, Chris.

Answer
If you have not missed any periods and have had two negative pregnancy tests and, in addition, have been on birth control pills, it is 99.9% sure that you are not pregnant. You cannot get your period while you are pregnant. YOu can, occasionally bleed during pregnancy, but it is not your periodl. The current pregnancy tests are quite accurate as long as you take the test seven days after your missed period. If you have doubts, take a blood test for pregnancy , 48 hours apart. If you are pregnant, there will be a doubling of the results in 48 hours. If you are not pregnant, each value will be less than 5. If the last time you had sex was June 11, and you did get pregnant on that day, you would now be 28 weeks pregnant. A sonogram would definitly show a fetus and your uterus would be felt 4cm above your belly button. I really doubt that you are pegnant.