Whats Wrong With My Rabbit?

A few months ago i noticed some scabs appear on my bunnies rear end.. they weren't bleeding or looked sore but i got her some shampoo and some cream for itchy spots and wounds etc.. but it wasn;t till yesterday that i noticed they had become really sore and had spread to her hind legs / spine part of her back.. i bathed her and put some cream on but im not sure what it was. i firstly thought it was fly strike but there was no sign of maggots or bleeding.. so im guessing it might be a flea allergy or maybe shes illgeric to something? but im not sure what to do.. does anyone know costs for vets for a rabbit or got any advice. thankyou!