Today I had one small cup of black Tim Hortons coffee. I then felt high for four hours. Could I be allergic?

This is a repeating theme with me. Anytime I have coffee- I feel dizzy and I can't focus on anything. I think I am literally "high". Also, I sweat from every pore of my body, including top of arms and legs. Dripping. I do not drink soda, but I do have dark chocolate occasionally and do not experience this effect. Whats amazing is the small amount of coffee that produces this effect. It was only about 8 ounces. What is going on? Can someone please help me figure this out? I still feel weird right now- it makes it very hard to write or study- I can't concentrate.