Why is it that every time I drink my tolerance is different?

Ok, so this is something that has been bothering me for quite a while now. For reference, I usually drink about 2-3 times a week, and I’ve been keeping up this habit for many years now (fluctuating, of course). However, I’ve noticed throughout the years that every time I begin to drink, I can never predict how drunk I will become. I’ve tried taking stats (food consumption, exercise levels, the social setting I’m in, how tired I am, what time it is, what I’m drinking, what I’m mixing my drinks with, where I’m getting my drinks from) but no matter what, my night is unpredictable.

It’s become quite bothersome as I am getting a bit too old to be worrying about this kind of thing (I brushed it off when I was a teen and just attributed it to…being a teen) and can never regulate myself. When I talk to friends, they always know their limits and such, but when they ask me, I can never produce a solid answer.

For example, there was a day recently where I had about 7 shots before I went out and I felt way too sober (I was surround by drunk people and felt like the most sober person there, which I was not trying to be, tbh). But, there was also a day last week where I had about 3 shots and was very happily drunk and content. These are, of course, only two instances I am recounting as a reference, but my shot-to-drunkness ratio changes literally every single time I drink. Also, it’s important to remember that I am tracking my stats to see if there is a pattern— there is not one I can find.

So I guess what I’m asking is, if there are any very wise science-y people out there who feel like they might have an answer, or if there is anyone who has gone through the same thing and found out wtf was going on— I would love to hear your take. I’m also just very frustrated that I never know how much I can drink on any given day.