guys.. what if he’s actually cheating on him or doing something just as bad..?

Nah BL doesn't work like that. The ML never cheats. (In stories like this at least)
Actually I can relate to him cause I keep personal stuff/troubles to myself too. I'm not comfortable atm to open up to people or tell them much about my personal life.
ML probably has some kind of past trauma which keeps him from opening up to people and as always must be something to do with his probably rich ass family.

Clock itヾ(☆▽☆)