sometimes i’m a weekend warrior, sometimes i can’t have half a shot. HELP?

i’m turning 21 on the 27th, and the day after i’m going home for a short visit with my best friends. the issue is, i don’t know if i can enjoy it the way i want because my physical tolerance is so finicky.

sometimes i can drink like normal and just have a few hours hung over the next day, if any at all. sometimes i drink a single shot or seltzer and two hours later my stomach is cramping and im sweating till i make myself throw it all up. i don’t get any hives or itching like ive seen for normal alcohol intolerance/ allergy. i have no clue what this is or why it happens, i always make sure i have enough to eat before but it still happens seemingly randomly, i know i need to go to a doctor to really get to the bottom of it but i don’t have time before i travel.

i barely drink (partially because of this issue, mostly because im just a social drinker), but i really wanna be able to partake with my friends, especially because one also just turned 21 this month. i know it sounds dumb but id like for it to even be an option. if anyone else has dealt with this, id be interested to hear about it!