What Causes Abdominal Cramps, Headache And Nausea With Negative UPT?

I have a lot of the symptoms of being pregnant, I took a pregnancy test and I am not pregnant but I have no idea what s going on.. I had a scare with my gallbladder awhile ago but they ruled it out after the x-rays. They told me I had abdominal migraines, and I had all the symptoms but I ve been getting horrible headaches in the back of my head on both sides right behind my ears. I feel tired all the time and nauseous. I have taken tums and antacids, even ibuprofen, but nothing will help. I even gave up on pop and have been drinking water, nothing is working and I have been feeling horrible for a couple weeks now.