On Giving Head

Okay, so I've never really had any complaints about the way I give head. Most guys are just super pumped to be getting it. However, the past few men I've been with have been larger and enjoy things like deep throating. I'm pretty inexperienced when it comes to that and actually the last time I tried the guy was too pushy about it and I puked some. so embarassing. also I hate letting guys cum in my mouth because you never know when it's going to taste awful and it's never really good anyway. I'm frustrated because I want to please my partner but I also hate gagging on dick. back when I was with men who were easier to please, I loved giving head and now it's just stressful... anyone have tips??