I'm sorry to hear you are not feeling well! Just to let you know I am not a doctor, but am giving you this information based on what I have researched and based on my own knowledge of this topic.

Here is what I found:

Symptoms of caffeine overdose:
Symptoms in adults may include:
•Breathing trouble
•Confusion
•Convulsions
•Diarrhea
•Dizziness
•Fever
•Hallucinations
•In and out of consciousness
•Increased thirst
•Irregular heartbeat
•Muscle twitching
•Rapid heartbeat
•Sleeping trouble
•Urination - increased
•Vomiting

If you are still feeling any of these symptoms I would call The National Poison Control Center (1-800-222-1222) (for the U.S.).
These are the side effects I read for caffeine intake:
Dizziness; irritability; nausea; nervousness.

To me, based on what you have written, it sounds like it could be from too much caffeine but the headache and loss of appetite could be caused by other factors or issues too. If your symptoms haven't progressed to something else, but are still present, I would keep monitoring how you are feeling and if you continue to feel these symptoms (or especially if you are feeling worse) then I would call a doctor, 911, or go to the emergency room. I hope you are feeling better!