What Causes Sickness, Nausea, Headache And Balance Loss After Alcohol Ingestion?

Hi, I am 21, small and slim so I can t handle much alcohol. I went out on Saturday and was very drunk, I ended up being sick all of Sunday but usually my hangovers last for a day but then when I wake up the day after I m fine. However, I have felt very weird since Monday, I have really bad nausea with a headache, I feel off-balance and like I m going to fall down every time I stand up. I also feel like I need to be sick constantly although I am not able to. I m not sure whether or not this is related to the alcohol that I had as I have never felt sick so many days after drinking, even when I have drunk a lot more in the past. The sickness is not a familiar feeling either.