Does anyone know what this is?

My cat, Brandy, is almost 3 years old. Last summer she developed small bumps on her face, head, neck, and other areas of her body. It went from just one to several and she pulled out a lot of her hair. I took her to the vet and they said she was likely allergic to ragweed/pollen. After they gave her a steroid shot she became better, but weeks later the same thing. This last trip to the vet was even more frustrating. Because she had received so many of the steroid shots (3-4) I decided against giving her anymore because of the risk of diabetes. We changed her food to a limited ingredient diet brand and she has been on a daily oral antihistamine. She has fewer bumps, but a noticeably larger hair loss problem and it is a concern that she may be slightly constipated. What could be wrong with her? 

My guess would be allergies.  First, I would get a second opinion if you don't want to give the shots that your vet suggested.  I know a women who's cat gets allergy shots every season.  Sometimes, cats who have allergies are also given a regimen  of prednisolone tablets that may help.  This is if your kitty has allergies.  Please, I'm no expert.  If you do get a second opinion, look for a "kitty" vet.  That sometimes is a better option for difficult to treat problems. 

I would get another opinion from an all CAT vet if you can. It does sound like allergies but there are other options available. Have they done a skin scraping type test to rule out some type of mite( or other organism ) ? Does your kitty scratch ALOT. , sneeze, and cough ALOT? Good luck