Oh my goodness! That is a lot to take in!!!
Do you have homeopathic doctors in England? (That is where you are, right?) If you do...I would think about seeing one of them instead of a regular mainstream doctor. I've lost patience and faith in regular doctors and simply use them as a tool to help me with some of the harder things I need diagnosed or for those times that we actually need medication. You simply do not brush me and my concerns off as heartburn or constipation....especially after I've told you that never once was there a single instance that made me think heartburn and the medication that was given last time did absolutely nothing....and NO that doesn't mean give me a higher than normal dose! Now...if they hadn't been GUESSING and had run actual tests and spent more than 5 minutes with us then maybe I might be willing to listen to that.
But anyway....at this point I would be doing a major elimination diet to see if that helps and to get a good grasp on what you can eat. Once I got that under control (hopefully with the help of a good naturopath or something) I would work on figuring out what vitamins and minerals I was deficient in and start working on getting those into my system. Maybe add a good probiotic once you have that all under control.
Either way....huge, HUGE hugs to you! Wish I could be of more help. Maybe look into the Paleo way of eating. It avoids all grains and it sounds like it would be a good idea for you.