Very bad pain after drinking

Im a 22 year old active female. No healt problems, except for some anxieties. Got a full blood test about 3 months ago, everything was PERFECT, all my counts were where they needed to be or even better. Also tested my thyroid (far anxietys, i thought maybe its due to hormonal imbalance ) eveything is good there. For the last 6 months, after drinking a night before i wake up with the worst pain in my stomach, top to bottom, front to back. It feels like my kidneys, my liver-everything hurts very bad . Im not a heavy drinker i usually have 1-3 coctails, or a couple glasses of wine. The pain is especially bad in my back. I recentlly became a vegetarian and im wondering does that has anything to do with these pains? Maybe there is not enought fat or protein in my body ?  a year ago, i used to have a lot more drinks and i was perfectlly fine the next morning.
Thank you for your answer:)