no dude that's really manipulative of your boyfriend. like what did he do when he was single? you don't have to have sex with him even when you're feeling well, let alone when you're ill. combined with the way he treats you in the rest of the relationship (ignoring you except for sex, avoiding you, blackmailing/threatening you) I'd say he was being abusive, it sounds incredibly unhealthy. I don't know the situation with you and therapy, but I can guess that it made you a happier and more confident person and he decided he didn't like that so is trying to beat you back down again. even though he says he loves you, this relationship isn't good for you x