Em - you poor thing, I had something very much like what you are describing 8 years ago just after my husband had a heart attack (survived thank goodness) Looking back I think my whole body must have gone into shock, the pains were griping in the same places as yours, I felt nauseous every day, I was shivering too and had an awful pain in my back but mainly near my hip bone which restricted me walking. I had every test under the sun, they wondered if it was my kidneys but found nothing amiss there, the pain in my back was getting unbearable so they sent me to an NHS Osteopath based at our local surgery. I had never been to one before and he was so rough with me, seemed as if he was punching or standing on my back. This inevitably made the pain worse and I ended up barely able to walk for 3 months - I honestly thought my time had come! It was suggested to me that he had made things worse by bruising the psoas muscle. My GP was very kind and after much deliberation decided to try me on Mebeverine (Colofac) to calm the tummy and back spasms down as he thought it could be a severe case of IBS but not with the "normal" symptoms. After a few more weeks these tablets gradually worked wonders, and I'm glad to say I haven't had this as bad since, but Em it does sound as if it could be IBS. I didn't have diarrhoea all the time as is one of the symptoms I just had the debillatating pain which completely wiped me out, really scared me to death, and left me exhausted. Please ask your GP if you can try Colofac, one before meals calms everything down - believe me!
I trust you will feel better very soon, you really have my sympathy ...... xx