DrJ, I have just done the same thing for (possibly) the same reasons.
I usually drink 3 – 5 mugs of black Aeropress filter per day, which led to, well… er… erm, well…..you know 😳
I cut coffee out completely for a while and it was like a switch had been flipped, everything back to normal (such as it was).
I didn’t get caffeine withdrawal headaches (IIRC it’s thought that the cause of the, er, symptoms, is not the caffeine per se, but something else in the coffee – IME decaf filter also has similar effects) but I did feel completely and utterly knackered despite substituting it for tea.
In the end I have reintroduced coffee just to alleviate the constant tiredness, but try and limit it to two mugs a day, and that seems a relatively good compromise.