Giving head to someone uncircumcised??

I've never been with anyone uncircumcised until my current bf. Usually I'm really good at giving head (I don't really have a gag reflex), but I struggle so much with him because he's so sensitive that if I pull back his foreskin it feels really overwhelming and weird for him. I've asked him what he likes and he's tried his best to communicate to me, but whenever I get a good rhythm going and it seems like he's enjoying it I accidentally move his foreskin and it's game over. I just really want to give him amazing head like he does for me 😭 Does anyone have any experience with this and have any tips on giving head to someone uncircumcised?