Drinks hit me all at once hours later

So basically, since last year, alcohol now takes about 3 hours minimum to take effect on me. This has been really hard because I feel completely sober at the function then 2 minutes i’m black out drunk. Even though I pace myself (one drink per hour, usually a beer or a single shot margarita that i nurse) this keeps happening whenever I drink (maybe every other weekend?) and I don’t know what to do. The only way I could describe this is like as if alcohol were edibles, no buzz, no drunkness then all at once.

I’m 22f, 5’6 and 140lbs – I’ve never had any surgeries or anything; does anyone else have this problem? I want to feel buzzed at the function and also not blackout, any ideas?