I'm Having Some Weird Feelings Going On In My Stomach.

I'm having some weird feelings going on in my stomach. Started with fluttering then increased to pain. I've taken two pregnancy test and both say negative. Then the pain started to get worse which ended up in extreme back pain and heavy pains when I have to urinate. When I urinate it does not burn, but if I wait to long to pee it hurts. Now I'm feeling some pulling sensations in my stomach as well as having diarrhea a few days ago. What could this possibly be?!