Please tell me if y'all think I'm pregnant. I'm 16!

So I had unprotected sex about two months ago, but I have had one period but now my second period is a week late and I'm having no PMS symptoms, but I've been constipated and havin stomach pain when you push down near my belly button. I've also been nauseous and have had no appetite... I am 16. Is it possible that I'm pregnant? I've been unbelievably tired also. Also my period that was not late, came 1 week after the unprotected sex. We were using the withdraw method... I don't think anything got in, but we had sex several times that day, not to mention pre-***.
The period that came was very light and only lasted 2 days