I'm sure that coach and I would hate to lose you as a rowing buddy. But maybe there's some sort of chronic condition? Rowing is a very stressful exercise. My 77-yr old friend permanently incapacitated his right arm last year by trying ice skating...and taking a bad fall. Wouldn't like to see that happen to you.
Used rowing machines are selling for good prices
around here. Maybe you'd be better off with some other machine