This is normal. If you have any pain in your eyes, see your eye doctor. When you first start wearing contacts, carefully follow the break-in schedule prescribed by your eye doctor. Be sure your hands are clean before you put in or take out your contacts. Do not wear your contacts while swimming.
Soft lenses absorb chemicals from the water.
Gas permeable lenses will float out of your eyes. Most contacts should not be worn while you are sleeping. Sleeping with your lenses in your eyes may damage your eyes by keeping the cornea from getting enough oxygen. Also, it may put you at risk for infection. For extended-wear lenses, follow your eye doctor's recommendations for the length of time you can safely leave the lenses in your eyes.