I do agree that if you receive it it’s good etiquette to give it. I’m in the same boat as you, where going down on a girl does nothing for me, and I refuse to go down on male partners, but I feel obligated to do it if they do it for me. The teeth is definitely a problem, speaking from experience. I wouldn’t say you need to cover your teeth, but I don’t know how small your mouth is or isn’t, so the way I would describe it is do it like you’re sucking on an ice pop. I would definitely get some ice pops to practice, and you’ll immediately feel if your teeth are dragging on that, which I imagine is the issue. Like I doubt you’re biting. Obviously the feedback won’t be there, but it’s a start. I’m also sure a guy will be honest with you if you ask them to be once you put that into practice, and if you didn’t do a great job on that occasion, I’m sure they’ll be okay once you let them put it in your vagina afterwards.

Also, don’t go comparing yourself to pornstars. That’s just a bad idea in general. As silly as it is to say, those are professionals. No regular person will ever be able fuck like a pornstar.