My advice is similar to Tasha's, I would head to the doctor. Whenever I have a headache that medication isn't touching I go to the doctor.
I don't touch Excedrin with a ten foot pole. The one and only time I took it, it triggered one of the worst migraines I've had. It has caffeine in it (without a narcotic like codeine) and it caused my blood vessels to dilate so fast that it knocked me flat on my back.
I would hazard a guess that you're experiencing a rebound headache - though I have no medical training, just experience. The rebound may also have triggered a migraine.
I like you suffered migraines as a child and then they disappeared. Suddenly in my mid twenties they returned and have steadily got worse.
In the meantime we have a medication in Canada called Robaxacet that is a combination of a muscle relaxant, Tylenol and something that makes you sleep (no narcotics though). I like it from time to time because it lets me sleep and breaks the cycle. I'm not sure if they sell it in other countries. In the US I always Aleve Gel Caps - though don't overtake them. This is naproxen sodium and works pretty well, especially if there is any muscle spasms related in your headaches.
But my overall opinion is go to the doctor. Don't try to self medicate anymore. I've done that too much and done more damage than good. I've ended up with more pain in the long run trying fix the problem with over the counter medications and end up with rebound headaches.
Coquitlam55 (aka Nicky)
"The world is full of suffering, it is also full of overcoming it." --Helen Keller
I try and remember this each day I have a headache that I'm not sure I can overcome.