Advice for gag reflex?

Okay so this is pretty embarrassing. I almost never give head because my gag reflex is the worst. It takes about 2 min for my eyes to start watering and i almost throw up! I've been dating my boyfriend for almost a year now and I think I've given him head *maybe* twice. He says that it doesn't bother him but I know it does. He makes little jokes about it and I really just want to do this for him because he is the sweetest guy I've ever met. I need help, please! All tips are appreciated!