Hey Fenway,
Dan's comments are fair.
Another thought could be yes you are decreasing your pred/steroids and its a part of the withdrawal and your adrenal glands taking over again (cant remember how long you have been on them).
However, if you are taking advil every few hours are you aware that pain relief meds can actually contribute to further headaches? If you are taking them regularly for a prolonged period your body becomes used to having the regular dose (same can apply to any med really but headaches you will find are a common side effect listed) so once the level drops in your bloodstream it starts to yell for more again and compounds the headache by doing this.
You may have to tough it out and see if this is the case - sorry. You might feel my thoughts dont apply because you haven't been taking them for very long or maximum dose allowed or some other reason.
Just thought I might throw my hat into the ring anyway and see if my ponderings help.
Pred is horrible stuff - I am on it myself again and hate coming off it as I suffer flu like symptoms with really bad muscle aches and pains, sweating and exhaustion.
Thinking of you ((hugs))