Helenkathehedgehog, please be careful about giving advice as such a new owner, especially with possible health issues.
Bald patches are never normal and you need to go back to the vet. It doesn't have to be an exotic vet the vet you got the antibiotics from would be fine to see. Sometimes antibiotics can upset the natural bacteria balance on the skin and this can allow yeast or fungal infections to bloom. This needs to be treated by a vet.