Help idk what to do!

So my period was suppose to start on Halloween the. It didn’t I didn’t think anymore about it bc my periods are sometimes late but, took a pregnancy test it was negative. So I waited till Saturday night took another one negative started having a upset stomach stomach pains and going to the bathroom a lot. It finally stopped I started having pain on my left side of my pelvis area just thought it was from my upset stomach went to bed woke up with the same pain but off and on now it’s starting again. I know you have cramps and back ache from being pregnant but this off and on pain on just my left side is freaking me out!??!