I wear contacts, but recently my left eye turned dry with redness around the iris. What could it be?

I wore my gles for approximately 2-4 days, which lessened the redness; however, today I started school and I wore my contacts, but it got severely red and feels dry (doesn't hurt at all though). I saw the optometrist but she said I just had some really dry spots. I'm using a prescribed lubricant and I also got some eye drops. Any other suggestions? How long do dry eyes usually last?