Improving gag reflex?

I loveee giving my bf blowjobs but I have a terrible gag reflex. I know he finds it hot if I stuff his entire dick in my mouth lol but I really can’t do it for more than a couple strokes at a time or I might actually throw up on his dick. Today, he tried pushing my head down and don’t get me wrong, I think it’s super hot, but I just can’t do it. Has anyone figured out a way to improve their gag reflex??