Well snap Callum is the same in fact he screams so much a neighbour even commented she lives 2 door down!!!!!!
I have tried everything!!! Even asked for help from HV as Callum aged 3 still has craddle cap and needs to wash it, her words were dont push it as you could create a phobia!!! Do it as little as often. I do this with Callum and when i do have to do it found the best way is sitting him on bottom in bath full of water giving him a dry flannel to hold over his eyes while i wash hair using a sponge, i wipe it but not using to much water and a small amount of shampoo and although he still hates it doesnt scream just sobs.
Hope this helps and you understand it lol