Are you drinking caffeine throughout the day consistantly? Or, just in the morning? Do you skip your usual time to drink caffeine sometimes? Meaning you drink it later in the day than usual? Withdrawal headache from caffeine is more typical then getting a headache from caffeine. Missing your usual caffeine time, it can take as little as 5 hours for the headache to start in my experience, or you might not feel it for a good 12 hours.
You say the pain is left of center, and then you said center, I’m not clear on your answer. Towards one side can mean migraine, but you didin’t complain about other migraine symptoms, so I am going to stick with regular headache assumption for now.
My suggestion is you have to decide toneither quit caffeine, or be committed to drinking it on a regular basis like medication. Do not underestimate how much caffeine affects the body. If you decide to quit, the first few days will suck. The headache will be bad (you can take ibuprofen or Tylenol) and you will fall asleep everywhere most likely. Do not just quit the caffeine cold turkey, decrease your intake for several days until you actually go to zero.
If you decide to just reduce your intake, you will feel crappy probably even doing that at first. I actually feel under the weather and people come up to me for several days asking me what’s wrong.
Being free of caffeine has been more positive than negative for me (I quit about 15 years ago, sometimes I cheat fir a day, sometimed the cheat goes on for a week or two, but then I go back to no caffeine for months, sometimes years before I cheat again. I do get low levels at time from chocolates I eat).
Obviously, caffeine might not be what is causing your problem though, there could be something else going on. Hard for us to know.