As you are wearing contact lenses for such a long time period, you might be have developed dry eye
problem. Continuous use of contact lenses reduce the natural tear fluid in our eyes. You should start with an artificial tear drop ( like TEARS NATURALLE II , 3-4 times daily on both the eyes for 2-3 weeks). You should reduce the use of contact lenses during this period.
In the mean while you can check with an ophthalmologist for further evaluation.