Want to give BJ but have bad gag reflex. help!!!

Before we got married my hubby said he loved to get BJs. We waited to be intimate until we got married. The other day I wanted to give him a BJ (my first ever!!) but I was having trouble. I have a small mouth and bad gag reflex. He said not to worry about it and said I don't have to do it, but I want to be able to please him. I mean, it's only fair since he goes down on me every time. Any suggestions?