I'm so sorry you're feeling so lousy...you sound a lot like me, I've been really faithful to the diet but just cannot seem to stabilize. You mentioned a doctor's appointment...have you been "officially" diagnosed with IBS yet? Or are you just assuming that's what you have?
Small meals is probably a really good idea, and I've found that taking a probiotic has really helped me. Sadly, I don't have a lot of suggestions because I'm in the same boat, the weight is just falling off me. I try and just squeeze something small in whenever I can.
Do you have any sort of painkiller you could try? Even just regular tylenol? Maybe it would take the edge of the cramping a bit and allow you to eat a little more?
I feel for ya...I really hope you feel better soon Kelly