I have had a lingering headache for more than 3 weeks now. No matter what I take, it just subsides it for awhile. I have a history of migraines, but I take Excedrin Migraine and it always goes away. But not this time. Just wondering what would cause a headache to last like this.

You could get a re-bound headache from taking too much Excedrine. You might have a sinus headache which Excedrine won't touch.

I's suggest taking some medication for a sinus headache like Benedryl.

If it rebound, you will have to go without analgesics, probably for about 3 weeks for the pain to go away.

With migraine, it's important to know your triggers. If the headache is different than your "normal" ones, then a sinus headache is a good possibility.

If this doesn't work, you may have a sinus infection. SO, you still should get evaluated.