I injured my rotator cuff in june. the doctor did an x- ray and a ct scan. both came back normal. i still have a lot of pain. how long until it heals.

Can take awhile: If you are in doubt, I would get another opinion. But I would assume that they recommended physical therapy and exercises- don't be over-aggressive

Usually an MRI: is the best imaging method to evaluate the rotator cuff. Do you have a contraindication to MRI e.g. a pacemaker? Xray will not visualize the rotator cuff at all, and CT is not very good either(unless it was a CT arthrogram)