Fern wants to know if he's barking up the wrong tree. I think he's aware that the various desires he's feeling right now aren't rational. He knows he's under the influence of his traumas, and Cal's abuse, and they're making him want things that he may not necessarily want for himself outside of that influence. I think a lot of victims are actually pretty aware of this, but it's part of the despair, right? You know this X factor doesn't actually matter, that it's a fiction, but you have a brain wired to respect it by this point. You HAVE to go through the motions, against your better judgment, against social mores, against all sense.
You can manage it in some ways, like a controlled fall, and that's what Fern's trying to do. He knows he and Cal are only a hair's breadth away from slipping into another, similarly devastating encounter, and he's trying to figure out if there are safety measures he can put in place for himself that would make it not-as-terrible as before. All things considered, I think Fern has pretty good self-control, if he gets support from other people. If he's dismissed and told to deal with it himself, his choice is to destroy himself, but if there's someone there for him, he'll gladly occupy himself with his relationship to that person. Fern likes being alone sometimes, when he needs rest or when he specifically needs to ponder something out, but he's also friendly & loving, and when he's given no outlet for that, he becomes profoundly depressed and haunted by a sense of worthlessness. He's obsessed with being "useful" to others, like a lot of abused people are, but ultimately what's underneath that is a very prolonged effort to find anyone to care about him.