My Partner's Dirty Little Secret

Hey everyone, so I've been with my partner, Alex, for about three years now. We're pretty solid and we both agree that we don't want to see anyone else right now. But lately, there's this thing he does that's been driving me wild. Whenever we have sex, he likes to pretend he’s tied up and helpless while I’m in charge. It started as a joke but quickly turned into something more intense for him. He loves it when I talk dirty to him during these moments, things like telling him what a good little slut he is and how much I control him. It sounds crazy, but the way he reacts makes me feel so powerful. Plus, we both get off on it big time. But here's the thing: sometimes I worry that maybe this fetish of his is too extreme or unhealthy. Maybe he needs to see a therapist? Or should I just be happy with how much fun we're having and not overthink it? What do you all think, am I being paranoid, or does this sound like something to be concerned about?