What could be wrong with me?

so i'm an 18 year old female with a healthy bmi, and a pretty healthy life style, but my body has some issues..i can't drink alcohol (even like half a beer) without getting a horrible stomach ache/diarrhea/puking. I used to be able to drink but this recently started happening. Also, my stomach in general is just weaker than usual, and i burp way more than the average person but i never used to be like that. I also get hot flashes randomly, and i'm too young for menopause. The last thing that is wrong with me is that i'm a grandma and seriously can't stay up late. Teenagers are supposed to have a natural clock pattern to stay up later but mine isn't like that at all..what could be going on?