Hi i discovered a painless rubbery ball under my armpit this was in late april the 29 day before my birthday ... not sure how long it was there before i found it but it's there and it's now june it's the same size hasn't grown doesn't hurt any iit is?

Check other places like your neck, other armpit, groin to see if there is any ball there and if there is get checked up by a clinician. The ball is likely to be a lymphnode that are collection of immune cells that may be activated by infections or cancers. The earlier diagnosis are made if it is cancer the better the prognosis. If it is infection it would go down by itself. Do you have pets?see MD