Help with my tantruming 5 year old...?

okwhere do i start, he's always been very strong willed, demanding things, and i too am strong willed and don't give in. He's had a few problems, hearing up and down, and subsequently speech problems. he's had speech therapy, but his hearing has gone down again, and although his speech is improving, its no as clear as most his age. He's having grommets put in in 2 weeks. Because of his hearing he shouts a lot, but also he is naturally a hyper little boy. last month he was diagnosed with JIA (juvinille idiopathic arthritis), and it says children with this can be "moody and difficult". He's having steroid injections in his knees tomorrow, and i do think this is worrying him, despite our reurance, but this past week it's been like the terrible twos but worse! everytime i say he can't have something, or remove a privilge because of behaviour he screams the place down, the neighbours must think he's being tortured. I still don't give in an stay as calm as poss while the tantrum runs its course. just want any advice or reurance really. Also, i feel it gets him down, the amount of appointments he has to go to, as he wears gles too, he sees orthoptist, optitian, rhuematologist, physio, ent, speech therapy etc etc. on the other hand he's a very loving little boy, always telling my he loves me "more than anything else in the whole world" and cuddling and kising me!!! He can just turn at any moment! HELP!!!