Performance

So I’ve been with my boyfriend for only 6 months and during sexy times I always get so nervous to give him a blow job. I have a very small mouth and sensitive gag reflex. His penis is on the larger side. He assures me constantly it’s perfectly fine if I don’t want to but I like doing that for him. I’ve made progress getting used to it more and more finding my rhythm but I can’t get him to completion. He always says it’s fine but it bums me out every time that I can’t get him to that point. I can’t seem to keep a rhythm long enough to push him to completion. He is so caring and kind and reassures me every time that it’s okay but the more he comforts me the worse it makes me feel.