Tbh the only time that Dohyun acted a bit coercive about sex was when Sungho asked him if ...

Tbh the only time that Dohyun acted a bit coercive about sex was when Sungho asked him if they could do something else other than sex at the warehouse, like old times, and, Dohyun got that English book to "study" vocab on his body... but even then, u can see that he didn't force him to do it, he was just very unsympathetic considering Sungho had just opened up about his fears and concerns.
Other than that, Dohyun was just enjoying having intimacy with someone he was attracted to and made him feel happy and wanted. A rarity in his life.
It is unfortunate that Sungho interpreted sex something negative. The reality is that it was Sungho who introduced the sex to their relation and as time progressed and his mental health started going downhill, used it as means of controlling Dohyun into being emotionally dependent on him.
I believe that as their relationship progressed, Sungho wasn't having sex w Dohyun as an act of love amymore but mainly just to keep Dohyun manipulated. This is why he said that having sex with Dohyun made him feel dirty and disgusting because in the bottom of his heart he knew that what he was doing was wrong. He decided to blame Dohyun for it neglecting his own choices in the process.