confused?

Hi! So to start out, me and my boyfriend have had unprotected sex for the past month. I've taken about 2 pregnancy tests and they both said negative. The most recent one was 2 days ago. I've been feeling really shaky and kinda neasouse and I get shortness of breath, just  weird like I did right before I found out I was pregnant the first time. I haven't had cramps or any sign of my period that I normally do and I'm supposed to start tomorrow. I eat, not 3 meals a day but pretty regular. I've been drinking more of sprite and a little bit of water, but I never drink that much water. I drink like a actually caffeine pop a day now. I'm just freaked out about what's going on with my body. 🙄