You might not be ready to have sex emotionally. He says he can't because of school stress. It is certainly possible that stress could compromise an erection, but to say that stress can consistently do it, I would want to know more. I would want to ask some questions. Lust is very urgent, demanding, immediate, overwhelming and doesn't last for very long.
Love is more mutual and more simmering.
When you're in love, you have more concern for the other person. Love has long legs to walk a long way. There are a lot of specific places on the penis. The inner thigh, around his testicles, the entire pelvic region and the other 98 percent of the skin on his body is sensitive. You should stop having sex at 106.