Whats wrong with me? (About drinking)?

Ok so I'm only 16 and I've drank numerous times with friends and stuff. I'm pretty skinny too so I'm a bit of a lightweight. When I drink I never get drunk or anything easily. The worst part about it for me is while drinking I'll feel sick. Like I'll salivate a lot and I'll have to spit a lot and sometimes even throw up. Its so random too. Like the other day, I was at a party and I downed a huge glass of orange juice, vodka, jack daniels, and a brew mixed together (I know its a terrible mix, my drunk friend made it). And then earlier today, I was at another friend's house and me, him and another friend were casually drinking Heinekens. I got through half of mine and ended up throwing up. I was so embarrassed. Please tell me whats wrong with me.