Sometimes my eyes are blurry while wearing contacts, why is that?

Something in eye!!: Because you have something in your eye. Seriously this is the answer. It it also the same answer as to why contacts cause dry eyes, red eyes, discomfort, pain, eye infections such as keratitis, on and on.

Dry eye: Your description sounds like dry eye. Initial treatment is frequent artificial tears during the day, ountment at night, warm compresses a few times a day, and omega-3 fatty acid supplements. If no improvement, you should see an eye doctor for further evaluation.