Why does my stomach always hurt when I drink?

It doesn’t matter how much I drink, my stomach just starts hurting. I’d say my tolerance is pretty low since my first ever drink was when I was 19. I used to feel buzzed after only a little bit of 5% alcohol, but my tolerance has been increasing little by little.
I’m not a drinker and I don’t really enjoy drinking because of the stomach pain, but I’ll have a drink occasionally when I’m with friends. The weird thing is that no matter how little I drink, even just two sips, my stomach starts hurting, and suddenly nothing sounds appetizing anymore.
Just yesterday, I was drinking and already started feeling pain in my stomach. An hour or two later, I suddenly threw up. My boyfriend kept telling me I was drunk when I really wasn’t. I genuinely think I threw up because my stomach was hurting so much 😭
Does anyone know why this happens? I always make sure to eat beforehand too, so I don’t understand why I get such intense stomach pain from even a small amount of alcohol. And no, I don’t think I have gastritis cause nothing else makes me feel this sick other than alcohol