Wow. I have to admit that we've been discussing your plight and what suggestions to make to you.
Before I forget, I need to mention that taking pain medications (including Fenoprofen) more than two or three days a week can make matters worse by causing medication overuse headache (MOH), aka rebound. See Medication Overuse Headache - When the Remedy Backfires for more information on this. If you're in an MOH situation, nothing you take is going work, neither prescription nor "natural" medications. If that's the case, you need to work with your doctor to stop the medications causing the problem.
Checking the house was absolutely something you needed to do. Some other things to check include:
• If any pesticides or other chemicals have been sprayed in your neighborhood or someplace you and the girls go.
• Have you started using any new cleaning products?
• any new laundry products?
• any new perfume or other fragrance products?
• made any major changes to the lighting in your home?
I would also suggest that it makes sense for the three of you to see the same doctor. This is a mystery that really needs to be solved. You didn't say what diagnosis you or your stepdaughter were given, but I don't know if that would shed any light or not.
Please, DO let us know how things turn out?
Good luck,
Teri