Thank you so much for your reply, @CANDC

I’m not really upset, but more worried and sad.
Sad because my oldest son doesn’t seem to want to be open and honest with me anymore. Even if he has become a bit more social again, he’s still quiet in the mornings and evenings. I try to talk to him and ask if he’s okay, but it mostly feels like he just gets embarrassed.

I haven’t said anything about the diapers we bought, he’s taken care of that on his own. The only thing he mentioned was when we came home, he asked where we should keep them, because he was worried his friends might see them. He had the same fear a few years ago when he had problems with bedwetting. Back then he used a different kind, "night pants", and he was really scared that his friends would find out. We found a place in the bathroom, together with his brothers’ things, so he could feel safer.

I really wish I knew how he feels and what he is so worried about.
It’s hard being a single parent, there’s no one to talk to, so I’m really thankful that I can write here.