Ringworm, Kerion, Abscess, eczema

My son is 4 and developed a dry patch on his crown which itched, so I took him to the GP. They said it was exzema (he's had a few dry skin issues since he was a baby, but nothing that E45 hasn't cured). He was prescribed Dermax shampoo and a steroid cream. Within a week this area had lost hair and was red and inflamed. We were prescribed anti biotics and another steroid cream. Within another week, the area was bigger, red, oozing and painful, so we were given another load of anti biotics. Within another week the area was bigger, still oozing and had caused so much hairloss that he had a clear bald patch, so were given another lot of anti biotics and another cream (anti biotic & steroid). 3 days later it was definitely dryer (I wasn't having to wash his hair twice a day) but was bigger and more hair had come out.

The GP had stuck with infected exzema all throughout this time, and even when I put ideas in her head - abscess, psoriasis etc she dismissed them and said it was definitely infected exzema, yet this last time she said she was sure it was a kerion caused by ringworm and prescribed a medicine beginning with T which isn't licensed in children and has some pretty nasty side effects. I feel really worried and disheartened, cos I don't know why it's taken 5 weeks for her to suddenly change her mind and I don't think these tablets are anything to mess around with, so as she refused to refer me, we are going to see a private dermatologist tomorrow.

The lump as it stands is big (half a golf ball sticking out, but wider), it's red, slightly scabby and has zero hair on it, so he's basically got a very large bald patch. There is definitely fluid inside the lump, if I push on it, pus will come out, but not enough to reduce the lump. He has tiny little scabs all over his scalp which I'd say are new, but he's always had cradle cap/dry scalp issues, but these are definitely raised scabs so maybe associated!?

There is no medical history that I think is relevant, other than the cradle cappy scalp all his life, so would've logically made sense that he could get an infected bit, but the ringworm diagnosis is suspcious to me. Oh, and he also had a perineal abscess when he was a baby, which had to be drained under general anaesthetic, but the GP dismissed any connection with what he currently has.