Do I just have to deal with this for the rest of my life?

I've had chronic headaches for about 4 or 5 years. It's pretty much just been one headache since a couple years ago though. I've gotten a CT scan and an MRI, but they didn't show anything. I've seen my regular doctor and a neurologist. I tried three different medicines: depakote, topamax, and propranolol. None of them worked. OTC pain relievers don't work either, they don't even really help at all. I take Zyrtec (sometimes Zyrtec-D) and flonase year round for my allergies because my headaches always get worse during allergy season (spring/summer). But they just reduce the headache to what it usually is. I've tried acupuncture (I got about 4 or 5 treatments), it helped a little bit, but not enough that it's worth the $100 it costs. I went to a chiropractor for a while, but that didn't help my headaches at all. I got tested for allergies but I'm not allergic to anything they tested for (it was mostly food and stuff). I've tried different relaxation techniques but those don't really help either. I take a vitamin every day (it's B stress complex or something). I eat a healthy balanced diet and exercise regularly. I don't have much caffeine or sugar. What else can I do?