Okay hon, now that I'm actually on a computer rather than my phone, maybe I can actually get a more meaningful reply out.
First, take tonight to scream, cry, kick, punch (pillows!), throw things, whatever you may need to do to get your frustration out. Heck, take tomorrow if you need too. Get it out. Let it all go so you can come back to everything with a clear head and start really trying to understand it all. Right now, emotions are overwhelming. You probably feel let down... dejected as I put it. Hopeless. I promise you, you're not. We'll walk this walk together and find answers somewhere. No matter how long it takes, I'll stand beside you and we'll find answers.
Second, don't hesitate to question. Write them down. "Well, if it's this, how does that fit in..." and stuff like that. Just tonight, I remembered something from my mom's wedding 3.5 years ago. The day after, I was rushing to the bathroom and commented to my grandmother something like, "I must have a spastic colon or something." I don't know if it fits, but it's worth discussing with the doc. It's worth it because it shows there's more history than perhaps even I was accounting for.
Also, remember the tests don't show everything. Look into the SBFT, but even if that doesn't show anything, don't be discouraged. I was last year after I had mine. My colonoscopy had already shown some abnormality. Granted, I don't know what we're taking that for now, but whatever... that's not the point here. Anyways, I'd had a small bowel series of Xrays done, and they were normal. The doc told me that he doesn't put too much into that. A positive test means yes, it's definitely there. A negative test doesn't necessarily mean it's not. Much like a home pregnancy test... false negatives are possible. False positives are not.
See if they can do the capsule endoscopy. It's possible something is going on, but it's in that nether region that neither an endoscopy or colonoscopy can reach. From what I've gathered, only a capsule endoscopy can give you a view there.
Keep notes. It's hard for me at appointments to express exactly what this does to me on a daily basis, but notes may help. A journal of some sorts to record symptoms and such on a daily basis.
It's not all in your head hon. The answers are somewhere they just haven't found yet. But they will. And I'm here fighting the fight with you while they look.