Giving Head

I need tips on how to not gag when I give blow jobs. I’ve like giving them but I can never get more than half into my mouth bc my gag reflex is so bad. It embarrasses me when i’m trying to be sexy and please my man then start to gag. I know he doesn’t mind(bc we’ve talked about it) and respects me enough not to make me feel bad about it. Like i said earlier I like giving them and think it’s fun but I can’t stop gaggin. Help!!