deep throating!!!???

Girls I need your help...so my bf of 2 1/2 years was telling me he wants me to deepthroat. We've done everything in the book so I'm not new to anything, it's just that when I do give him bjs it can only go so far without me gagging. I've tried not to but it almost seems impossible when he pushes it in more 😩 any tips & or tricks for deepthroating ladies???