When your back gets rubbed, it probably eases up the tension in your upper trapezius muscles (between the neck and shoulders) right? If your neck gets a good deep message does this help at all? If this is the case I would look into trigger point physical therapy.
Have you tried triptans (eg imitrex) for a quick fix?
How often do you take OTC meds?
Does the pressue get better or worse when you lay down?