Hospital can't diagnose whats wrong with me?

What should i do? I've had a colonoscopy, gastroscopy, barium x-ray, ultrasound, blood tests, stool sample as well as various medications incase its IBS and they still can't diagnose me and said theres little more they can do for me. Please answer im desperate. These are my symptoms. I've been ill for 3 months now with a stomach ache almost all the time, my appetite has gone, im struggling to eat and i've lost 30lb now. Im also exhausted all the time, im not normally a lazy person but im needing around 15 hours sleep a night now. Also sometimes i feel like i need the toilet but nothing or some mucus comes out (sorry i know thats sick) and i had diarrhoea until a few weeks ago, im not lactose intollerant, im not stressed and i've hardly been able to leave the house for 3 months. Im 21, dont smoke or drink and was very fit and healthy before i got this. What more could i do? Thanks a lot