I have a weird situation.

My fiancé (21m) and I (22f) have been together for three years, and the sex we have is phenomenal. Well.. only when he initiates. For context, my partner identifies as being on the asexuality spectrum. For him, drive is low and he doesn’t always think about it, but he really enjoys the feeling during the moment. And when he is ready to go, it’s always great. I don’t really initiate because I want to be respectful of the fact that it’s not always what he’s in the mood for. And honestly, having a relationship that isn’t based around sex is one of the best things I’ve ever had.

But, here’s my worry: he knows that my drive is rather average to slightly high. He’s told me that whenever I’m in the mood that it’s okay to initiate. I’ve tried only a few times, but whenever I initiate he gets tired/cramps up after a few minutes and taps out or simply doesn’t finish. We are rather vanilla too, so it’s not an abnormal amount of exertion coming from either side. Though, it makes me wonder if I’m doing anything wrong or if I’m just misreading a make out session. Because I know it’s not that he doesn’t want to, as he used to initiate very often, and it was always incredible for the both of us.

How should I go about talking to him about this without hurting feelings? Or, should I talk to him about it?

Edit: I want to add that I don’t want to end things over this. I wouldn’t have agreed to marry him if this was a dealbreaker. I just want to figure out what’s up without anyone hurting anyone’s feelings. Even if it results in him not wanting to have sex anymore, that’s okay. It’s not what I’m in the relationship for.