Have hard bumps on inside of both cheeks of mouth, hurt bad. They white reddish. Been like this for week. Hurts! What is I that can I do?

Bumps. Could be trauma from your teeth. Since you are on mtx could be from impaired immunity as well. Gargle to keep them clean ; get an OTC cream or spray for local pain control but go see an ENT or oral surgeon ASAP.