The first thing to do is make sure his mattress has a good waterproof cover on it. What to do next depends on several things that are not clear from your message. If he is able to wake up and get to the toilet most of the time, then a diaper might be in the way and make it difficult to use the toilet. A washable bed pad with a folded towel over it may be all that he needs in that case. If he wets the bed nearly every night then diapers may be a better choice, but you could also consider a bedwetting alarm or medication. The doctor that checked him might have recommended that. If diapers are the right choice, you will need to understand why he is opposed to them before you can convince him to try them. Many older kids and adults think diapers are only for babies and using them makes them feel immature. He might not have enough privacy to store them and use them without being seen by his housemates, and is afraid that they will make fun of him. Or, he might believe that using diapers would be an admission that he has a problem that he can’t control and he isn’t ready to do that. From messages I have read here, most college students that need diapers realize that it is impossible to keep their bedwetting and use of diapers secret from a roommate, so they don’t really try. Nearly all of them say that the roommates are understanding and don’t think much of it. If you do convince him to try diapers, make sure you get good quality ones. Cheap diapers that leak may make him think that diapers don’t help so why wear them. Most disposable diapers for sale in stores in the U.S. are not adequate for bedwetting; good ones have to be ordered through the mail or over the internet.