I know what you are going though. I am a diabetic (type 2), and a little over weight, but I'm trying hard to lose it. Over the past 9 years I've been getting bad abdomen pain, touble in the toilet area, feeling/being sick every time I eat, always sleepy ect, My GP wouldn't do anything about it and just kept telling me that it was down to my weight, and told me that if I lost weight all my problems would go away. How wrong he was. I lost 3 stone in 1 year and still no better. Due to this the depression I had got worse, and I lost my job over it, as I wasn't working as hard as I could of. about 4 months ago I told myself enough is enough and changed my GP as this wasn't being fair on my Daughter (who I'm bring up on my own). My new GP is great and is doing everything possible to help me. She has do so many blood tests on me, now i'm told I have underative thyroids, and one of my tests came back positive for coeliac disease. So I was sent to a Speacialist and saw him on monday (15/3/10), just to get kicked back down, He tried to tell me that just because the blood test came back positive it don't mean i have it, I have to have an endoscopy done on the 31st march which I am really scaried about (I have a fear of hospitals st the best of times), and he told me that all my pain and bits are all in my head and then started on about my weight. I was so cross that I was seeing red when I left that appointment. I am now going back to my DR and telling her that I'm not happy with this specialist and want to be put into another specialist. Maybe you should do this as well, Go and talk to your GP and tell him/her what happened and say that you want to see someone else. They are not allowed to blame everything on to peoples weight, I'm not saying losing weight wouldn't help, but it's not the only thing you can do, he should of been more helpful to you.
I hope this helps, Good luck mate and hope you start to feel better soon x