Extremely Lightweight and I don’t know why

6’0 145lbs and when I drink a few beers and a beatbox or two, I’m suddenly slurring my speech and stumbling around everywhere. My drinking buddies hate it because they have pretty good tolerances (it takes probably 5 shots for them to start getting tipsy) and I’m always the one to call it a day first. It’s gotten so bad sometimes that they think I’m faking it because of how little alcohol it takes for me to be completely smashed. How do I fix my crazy intolerance? If it’s any help, I’m of super mixed descent, with asian, native, and european blood.