W.O.W.
I don’t know how to say this nicely, but here goes. One other issue that you have to remember is that boys, starting from about 13, have a bit of “fire” in their blood.
He already feels that he doesn’t match up to other kids his age. On top of that he got these feelings that no one talks about (especially in frummer circles), so he thinks that either he may be the only one in yeshiva with them or just bad kids have those feelings.
I’m not sure about how to approach it. No teenager would want to talk about it with his mother. Subtlety is key.