I Can't Drink Now Like I Used to a Few Years Ago (26M), is that Normal?
During college and a few years after (maybe til 23/24) I drank almost weekly and don't get drunk that easily. In terms of beers, maybe I get tipsy at about 6 and give up at 10.
But now, I drink 2 and I get tipsy, and maybe tap out at 4/5.
It's fairly normal to suddenly find hangovers are a big problem as we get older... it feels like one day you're able to go out, knock back a hideous amount of booze, then bounce back the next day ready to do it all over again... and all of a sudden those two pints of beer create the hangover from hell.
Not sure about tolerance though. What country are you in... is it easy / cost effective to get a liver test done? It might be down to lots of perfectly natural factors... if you lost weight; if you have a different diet (some foods 'soak up' alcohol better than others and cause it to be absorbed more gradually, if you're drinking on a salad instead of say, pasta you'll see a difference); you could be drinnking different beers.
Also, if you've had significant weight gain, this causes your liver to get fatty, which puts a strain on it; I'm not a medical professional but would think that could have an effect too.