Why Can’t I get drunk?

This is bugging me really bad. I’m not an alcoholic. I tried drinking six months ago, but every time, no matter how much I drink, I never get drunk. I have gone through three quarters of an entire bottle of vodka and still felt nothing. I get dehydrated and experience headaches when drinking alcohol but nothing more. I don’t even get hungover. Right now I’m really curious about how being drunk actually feels like, since I’ve never experienced it.