Always gag giving head

Ca

So I hate giving head to my boyfriend because I always end up gagging before he cums. He has a high endurance and it takes a while to get him to cum. I have looked up several tips but he always ends up pushing me farther down then I can handle or it takes to long and I end up gagging. I’m allergic to latex FYI. Any suggestions on what to do. I know he really likes it and he wants to make it a little easier on me because he knows how I feel. I normally only do it for special occasions