What Causes Constant Headaches And Pain Behind The Eyes?

Hello, I am a 24yo male and lately iv had a constant headache. Its been going on about 3 weeks now. I wake up with it and go to sleep with it, feels like a constant dull ache like someone squeezing my head all over, i cant seem to pin point the pain but i feel it alot behind my eyes. Iv noticed it is worst at work or while im trying to focus or concentrate. I do work long hours as a tree harverster operator which takes alot of focusing and concentration, iv been doing it for about 8 months now and never had headaches before. Im always tired and Sometimes it feels as if my eyes go slightly blurry and i get slightly disoriented which is very frustrating at work and its really starting to effect daily life. The doctor says that its tension headaches and gave me some tablets and told me to do some relaxation techniques, 2 weeks later and I feel the same. Im going to the doctor again next week but just thought id get a second opinion. Im not sure if this is related at all but sometimes I also get this slight strange feeling as if iv got water in my left ear, and today iv noticed if I push rather hard on the roof of my mouth with my tounge I get a strange pressure sensation that kind of runs through my teeth and almost feels as if it links up to my headache. Any help would be greatly appreciated. Thanks