Absolutely it's a terrible way to live.
Keep searching, keep trying, and keep asking. I just wanted to encourage you that you DO have a right to be treated seriously by Drs- there will be an answer somewhere, somehow. Sometimes it is the non-medical set who can give you solutions (and funnily enough, medicine often catches up with these 'alternatives' and prove how they work!)
But give the 'simple' answers a go first. A relative of mine swears that if she has 2 pieces of fruit a day, everything is great, if not, it's not - like you, she's always had this propensity. Her little boy had terrible issues too, but he seems to have grown out of it (I think for a while he couldn't have bananas or cheese...it's a while ago).
Wouldn't it be great if the magnesium helped you out?
Probiotics help some people too, but it can be a bit trial and error to get one that works for you (expect some BAD reactions), and also believe it if you are advised to go on a tapered increasing dose - a very very little bit at first. Same approach with psyllium - if you jump straight in, it can make you worse. But just try one thing at a time, over time, so you know what is causing what