I'm confused feedback ??

Okay I know I'm not pregnant I'm always having safe sex with my boyfriend of three years now, never a scare. We always use condoms with the pull out method combined because I'm not on birth control and we're young, we also fill the condom with water to test it after. May sound bizarre but we're young better safe than sorry, I've only let him put it in for a short amount of time with no condom once. Everytime we have sex including that time I'm never in my fertile window or ovulating, but this month after that I had a period that came on time but it was lighter than normal but at times it was heavy like normal and ended two days early. I didn't think much of it considering the situation and I was under a lot of stress which probably effected my period. Just in case we did take two pregnancy test a couple days apart from each other both came back negative almost right away. No surprise to us but I've been having boob pain and slight acheyness and some heartburn lately, some cramping, I think it may be stress, but I need feedback why am I having preg symptoms when I'm not ?? My next period is due in 12 days .