Going crazy over here

Okay so my period was 4 days late, I started three days ago today it has been brown in color and barley anything. Before I started I had really tender boobs, gassy and still have that, light cramps, nauseous.

Today I have been just feeling really weird and off. I’m really nauseous and just feel sick. Idk if anyone else has gone through this before but it’s driving me crazy what’s going on. I took 4 pregnancy tests before I started bleeding and all were negative but I just don’t know.