Erection after heart surgery

My fiance recently had heart surgery. A little bit of background, we would have sex alot before this and like hours at a time. He had a really high sex drive. So we waited the three weeks the doctor told us to then he couldn't get hard no matter what. So then about two and a half months pass and he can get hard now but he doesnt want to have sex. He says that the urge is just not there anymore. Has anyone else experienced this? Maybe have any tips we were also TTC before this as well.