I was operated about 8 months ago and I can't really eat a lot of things, I usually get pain when I eat something. I get diarrhea after eating something. I've lost a lot of weight because I don't eat things that have a lot of fats like meat and stuff. When I walk I get dizzy and I feel like im out of breath and I have to go to the bathroom. My doctor says that the dizzyness comes from me being dehydrated because of the diarrhea, she tells me to drink lots of water but it still doesn't help very much.

Is this normal?
Does anyone else have any of these symptoms?
Does it have anything to do with the gall bladder? or could it be something else?
Thanks for the help!