This sounds really frustrating. It’s hard to know without examining you and taking a look at these cysts, but in general sebaceous cysts are harmless. They commonly occur on places like the scalp, ears, and back, as you are describing. They’re caused by blocked glands and hair follicles and people with oily skin tend to be more prone to them.
Often, sebaceous cysts will resolve without any intervention. If not, your doctor can drain or surgically remove them. There isn’t a great way to prevent these cysts except to wash your skin often and with oil-free soap.
If these are really bothering you I’d recommend you go see your dermatologist again to see if these needs to be surgically removed or drained, or if there are any other treatment options.
FYI, I do have pictures because its the only way. Can see what's going on. I just can't upload them here. Or I don't know how to