Deep throat?

He really likes it. But it hurts me and I gag every time. Not just gagging as in making the sounds. But like I actually could throw up on his lap if I didn't stop to swallow it back. Then he gets upset that I stop. He says it's because he's excited and doesn't even realize when he's hurting me. Are there any techniques to keep myself from gagging or make it not hurt as much? Do any of your men like it? And do you do it?