I have the same problem! I cannot handle caffeine to save my life! It makes me feel absolutely horrendous.

Recently, I had very little sleep as the neighbours had kept me up nearly all night with their party (lovely) and had to work a long shift. I literally could not keep my eyes open for the life of me, so I decided to get myself an iced coffee. I hate to drink coffee bc it makes me shit like there is no tomorrow (I have IBS) but it was an emergency and I really didn't want to fall asleep at work.

I felt like I had taken drugs and had a huge hangover at the same time. I felt nauseous, had a headache, got diarrhea half an hour after finishing, but at the same time my eyes where wide open, my hands were shaking, I couldn't sit still and I was having heart palpitations. While my brain still felt so tired.

I will never have coffee ever again.