What would be the most common causes/treatments for headaches that happen the same time each week?

Probably migraine: Migraines are the most common cause of recurrent headaches (ha). Otc pain meds can contribute to rebound/medication overuse ha which causes the ha to actually worsen in the long run. You should see a neurologist who can get you on a good preventative agent as well as a good acute agent (i.e. Triptan i.e. Imitrex) for the pain. The need for a preventative depends on the number of days of head pain.