Look, having sex twice in three days is pretty good!! No, it's not nyphomania, but still, that's a good amount of sex. I think it's
you who's horomones are a little bit higher than his. Next time you're together, wait, and let
him initiate sexual contact. Don't be afraid to suggest "let's do it off the side of the bed" or things like that once you get going, but make him start it. If he's bored with sex, indulge in other daily activities.
If he's not always expecting it, that can also make it more exciting. So if you start visiting, and not initiating sexual contact, a) he'll know he gets to start it when he feels like it, and b) your mettings won't be totally focused on sex. C), after this has been going on for a while, you might even end up not having sex at all during one of your visits. Next time,
you engage him. He'll be suprised, since you've been letting him have control the whole time!
Your relationship can be about more than just the sex, and perhaps this is a stage where you two need to focus on your out-of-bed expereinces together. Too much sex can make anyone bored, and perhaps twice in three days is just too much for him.
Is he older than you? He may be reaching a different stage of maturity than you as well. Does he have anything in his life that is stressing him out? That can also cause a loss of sex drive. Trouble in bed is often a sign of something from the outside influencing his mind and focus.