Almost constant headache and feeling of stuffiness in my head?

I have an almost constant headache and my head feels stuffy. I often feel groggy and slow. Water or just any liquid does help my symptoms. I generally only drink when I feel thirsty and I don't drink very much. When I press down on the tops of my eye sockets, just below my forehead, I feel pains in my skull and behind my eyes. I have no idea what this could be. The headache generally isn't too bad, it's just there in the background. I know people can't diagnose me over the computer, but I'd like to have an overview of what this could be and whether I should go to the doctor's or not.