Persistant bloating; no diagnosis?

[bkjo21]

For nearly 4 month, I have been dealing with persistent bloating/abdominal distension.  I wake up with a slight bloat and it get progressively worse throughout the day, even after I drink a glass of water.  I maintain a fairly healthy diet and exercise regularly.  I have been to several doctors including my GP, gyno, and GI-NP, and no one is able to give me a diagnosis.

A list of tests I've done and their results:
- abdominal ultrasound - normal
- transvaginal ultrasound - normal
- sitz marker tests (to see if I'm emptying my bowels normally) - normal
- blood work: celiac, thyroid, anemia - all 3 normal
- stool test - normal

My GP prescribed me an antibiotic Cephalexan just last week, I started taking it yesterday. I'm supposed to take it with a Diflucan.  And then yesterday by GI-NP called and prescribed me and antibiotic Flagyl (I haven't started it yet) but I read the reviews and am I little apprehensive.

Has anyone had similar issues and/or tried these drugs?