What Causes Constant Headaches When Taking Amlodipine Besylate And Lisinopril?

I have been taking Amlodipine Besylate 2.5mg and Lisinopril/HCTZ 10/12.5mg for the last 4 years- haven t had any problems. I have had a constant headache for the last 2 months, with no relief. I have seen an ENT and Neurologist, and neither or them see any obvious indication of what is causing my headaches. Could it be my BP medication? I am 39yr old male, 210lbs, 6 tall.