I think you'd better take off your contacts when you are going to sleep. Sleeping with contacts will cause many problems. When you get up next morning, you will feel like that your contacts are clinging to your eyeballs. And the discharges of our eyes may remain in the surface of the contact and cause inconveniences.
No, you can't sleep in your contacts. Our eyes are dry after wearing contacts for a long time. Our eyeballs are covered by contacts and canâ€™t be moistened thoroughly, so we need to take off contacts and moisten our eyeballs with some artificial tears. Sleeping in contacts will affect our vision too. So don't sleep in your contacts though you are very tired. It will not take you too much time to take them off.