Hi Lisa, welcome to the forum.
If you could post a picture that would be good, will tag Photo guru
@piggyfan to help with that.
This could be either mange mites or fungal, can you confirm what you have bathed with?
Either way he will need to see the vet for official diagnosis and treatment. He will also need pain relief. However, if he is attacking himself he may need a course of steroids in which case he would not be able to have an anti-inflammatory pain relief at the same time, so you would need to discuss that with your vet.
If mange mites (these cannot be see as are under the skin) I recommend treatment with Ivermectin, preferably by injection at the vets and not a spot on type treatment as it is more effective in advanced cases and less likely to irritate skin that already sounds very sore.
If fungal, please note that this can include more than ringworm (which is the only type a vet can culture for using the standard medium) I recommend baths with an anti-fungal shmapoo such as Malaseb (from the vets), or Nizoral followed by dips in Imaverol which you do not rinse off.
Here is the Imaverol link
http://www.hyperdrug.co.uk/Enilconazole-100mg_ml-100ml/productinfo/ENILCON/
Please note that for all shampoo and Imaverol he will need patch testing behind the ear for 48 hours. Also don't bath within at least 24 hours of any treatment with Ivermectin.
All baths and dips should be done weekly for 4 weeks.
If the fungal is really advanced then he may need oral medication too such as Itrafungol or Nystatin. Vets differ in the dosing for Itrafungol but my vet uses a regime confirmed by the company who makes it which is:
One week on
Week off
One week on
Week off
One week on
Basically it is a 6 week treatment as it carries on working on the week off.
I think that is the basics covered.