For a month I have had small itchy red bumps on both elbows and for 8 months I have had a scaly itchy rash under my butt, what could this be?

Psoriasis? Psoriasis involves both these areas and could fit with this description. There are many different prescription creams as wells intralesional treatment which can help this condition. An effective over the counter product to alleviate the symptoms is scytera foam. If the response is inadequate see dermatologist for evaluation amd treatment.
Many things. Rashes can be caused by many things. The areas where you describe the rash sounds like it could be psoriasis but you would need an evaluation by a doctor to determine for sure. Unfortunately rashes have to be seen to be diagnosed and treated. I would seek care with your doctor and if necessary, see a dermatologist (skin specialist).