I havent read all the replys, but in your 1st post, you said, the drs said he had a lump but it wasnt a hernia.
My DS1 has 2 lumps just below his belly button, that are always there, but also flare up and get sore- to the point of DS screaming. We have had ct scans, x rays etc and drs cant say what it is, just what its not.
I also see there is other stuff going on for your son. Maybe you could work out a routine that takes 2-5mins that you can do for him everytime his tummy is sore- and even have a home made "medicine" for it- a special drink etc that he can have. So he can have just few mins of your time- just you and him.

I hope you can sort out the physical from the mental soon, even though they are often closely linked.
- Our DS1 is also a sensitive child- bordering on special