The sensation you describe can happen when you do not have adequate tear film, or "dry eye." I would ask ophthalmologist to test you for dry eye and assess the fit of the contact lenses. If all is well with respect to tear film and fit, then you might try daily disposable lenses to eliminate possible reactions to solutions, protein deposit buildup, allergens.
I agree with above. Sounds like your eyes are 'tired' of trying to manage the contacts. Ensure you follow correct hygiene 100% contacts can cause many problems. If you have dry eyes buy a product that has NO preservative in it. The 'single use' disposable ones are the best by far. They have a small removable top though are usable more than once if you store them hygienically. Plus, make sure you blink enough. If you work on computers a lot you may forget to blink enough.