My boyfriend and I have always used a condom and i'm one of those girls that can predict the day that my period will come. In the past month I have been stressed with school and finals, went out of state for a week, gained a couple pounds and then lost them all in a short amount of time. So I figured that because of all these activities my period was late. But still my period hasn't come yet and the last time that I had my period was about 2 months ago. I have had two pregnancy tests and both turned out negative, one was 4 days since the last day I had intercourse, and the other was 10 days after I had intercourse. The clinicians told me that I had nothing to worry about and to let mother nature take care of it's course and that it was normal for a woman especially at my age (22) that a period cycle can change. But I can't help to think about me being pregnant, and if I am, how could this have happened? I know that condoms are not 100% accurate, but should I believe those pregnancy tests? Or do you guys think that i'm just stressing out and prolonging my period?

Ps: my breasts have been having these tingling sensations, and my stomach has been cramping a lot! Pregnancy or pms?