If you have one bloodshot eye for such a long time, there could be one of two or three reasons for it. One is that you have a busted blood vessel in your eye and it is showing up on the whites of your eyes. This is fairly common, and sometimes happens with the most inane of things. You can have a busted blood vessel in your eye if you have injured it innocuously. It could also happen if you have had to strain too hard for anything, from lifting weights to a bowel movement. Remember that the eye is an extremely delicate organ and has to be treated really delicately. If many months have passed, it may be possible that you will remain stuck with the bloodshot eye for the rest of your life. The only way to get rid of a busted blood vessel in your eye is to adopt an invasive method such as surgery. However, this is completely unnecessary and unless you are having problems, it is also a waste of money. Once the busted blood vessel has healed, chances are that it will simply remain there without causing a problem of any kind, so you are better of leaving it alone.
If this is happening to you intermittently over a few months, it could also be a case of eyes that are not well rested. Poor sleep, bright lights, staring at a monitor of some sort all the time, all of these are reasons why you could be having red eyes off and on. The solution is to remedy whichever reason applies to you. Additionally, you can also apply cool cucumber slices to your eyes for good results. Alternatively, you can also bathe your eyes with rose water. This will be an excellent solution to provide relief for tired eyes. Rose water is a cooling and soothing agent and is also good for your eyes. Another reason you could have this problem in one eye is also excessive alcoholic consumption. People who generally drink heavily also suffer from this particular problem. It would occur in one eye only because it is highly possible that one of your eyes is more sensitive than the other. In case you have delicate and sensitive eyes, you can solve the problem by resting them a lot. Try also to wash out your eyes before you sleep. Grit that is in the eye can cause pain while sleeping.