Cant take shots like i used to

I used to chug alcohol like water. I chugged a bottle of whiskey in 30 seconds i could chugg a beer in less than a second. After a few bad nights i can no longer drink a shot without throwing up or chugging a jack and coke like i could. I can still drink the same quantity and even more and be completely fine. I jusr cant drink a shot without throwing up . Also after 10-15 drinks if i even sip at my drink i get the urge to throw up even tho im completely fine fine not even drunk i just can take another sip. Why is this happening and how do i fix this