since swallowing is my advice I will offer a few off the wall thoughts.

Remember when you gag your saying "My god Master your big." That works wonders for me. Not all of us are straight of cock, mine is shaped in a curve like a semitar so a straight line is not great for us but it does make her feel like I have a very thick cock.

Throwing up is no fun and I agree not very sexy. I have to ask here are you being excited first by your Master so that your wet and in subspace or is he expecting you to just take it fairly cold. If so I recommend that he puts you deep into subspace first so hot and out of your mind that you are relaxed and willing for anything. Once he is in deep he should not be pulling out very far for that too will add to the gag response. Hold him deep as long as you can and swallow hard.

Yes your throat can be damaged but that is very rare and normally will heal given a little time.