I've recently, maybe, have a similar situation.  I didn't know that I had allergies and will be officially tested for them this week. I don't get a warning signal like runny nose or itchy eyes.  I had the same type of headaches...back of head, etc. as you described and around my jaws too.  For me it was diagnosed as a eustacian tube ear problem.  Allergies caused the ear infection in my middle ear and resulting eustacian tube ear problem, which might be an on and off permanent problem. Antibiotics (amoxicillan) is used initially to get rid of the infection. A nasal decongestant is the med for it day-to-day, either pseudoephedrine or OTC phenyleprine.  The anti-histamine helps with the allergy/initiating cause.  I can use a triptan, like Amerge, to get over the headache, but I can't take the Amerge everyday.  It'll cause rebound headaches and is $$ and the headache always comes back, along with the ear pain/ache/hearing problem(it can vary).  My eustacian tube headache usually doesn't become a migraine either, but it's a steady 24/7 headache.  Again, my doctor said I might have this ear problem on and off with that type of headache forever....  hope this info is helpful to you.