One time I gave up coffee was after surgery with a truckload of medication in me so I wasn't bothered. Actually I was more bothered by the 15 days of no food and just the danged i.v. drip.
Then another time I had to quit coffee for some kidney testing. I also had to quit a few other items and was just eating eggs and potatoes for a few days so that irritated enough that coffee wasn't a huge issue.
Last year (actually right about this time) I was advised to stop drinking coffee. The next 2 days were horrid. The headache, the nausea. Fortunately, I then developed another isssue which sent me off to the hospital where I was given morphine. It cured the headache and put me to sleep. When I awoke (the second time, not the first while a lumbar puncture was being done) the headache was miraculously gone. Naturally I returned to drinking coffee 2 months later.
I wish you the best in this endeavor as I have never been able to stay free from it. (gave up the booze and smokes but not the tasty treat known as coffee)