Queasy after drinking not much

So I drink heavily maybe twice a month on average and it’s usually shots but every time I drink even after just a couple shots I feel super queasy and even gag sometimes. This is without even feeling drunk yet, so usually I just go to the washroom and swallow for a few minutes then come back out and have more and I’ve never actually thrown up from it but it’s really annoying. Especially when I tried drinking two days in a row the second day I couldn’t get more than 3 shots down without almost throwing up and having to stop. What can I do to stop this from happening and why is it like that? I always eat before (usually pizza or smth).