"Medical problem with his, er, well, you read it..." joke

There was a guy named tom who had three balls, so one day he went to the doctor to do something about it, the doctor asked him

"how many balls have you got"

Tim was a shy person, so he said,

"er, your balls and my balls add up to 5 balls"

The doctor's face turned into a surprised expression and he said,

"WHAT???you've got 1 ball????"