Why am I so sick?

My stomach is on fire!

I am 4 days past my period (late/missed) I have taken 2 pregnancy tests and they are reading negative, so I doubt I'm pregnant.

I feel so awful. I have been sick for the last 2 days, like laying on the bed miserable sick. I'm not puking, I dont have diarrhea. I am having hot flashes though.

Any ideas on why I am so sick?