He's actually incorrect I think. As I understand it, FMLA can be used for chronic conditions and it can be used for follow up appointments if they are for the same reason for the initial FMLA. He does have the right to have your leave recertified every 30 days to make sure it is still qualified under FMLA. You might want to do a bit of research about the rules and have those ready as back up if this becomes a problem.