You can only sleep in contact lenses if they have been manufactured for this use. Contact lenses are made from different materials for many reasons and most are not suited for overnight wear.
If you do accidentally sleep in your lenses you may find that you wake up feeling like you have dry eyes since the lens is likely to have dried out considerably overnight (even though it’s been on your eye.) For the same reason, you may also find your contact lenses are difficult to remove. In this case, you can use some lubricating eyedrops and let your eyes and lenses rehydrate before attempting to remove them. If they’re still stuck, you feel like you’re not sure if you have a contact lens in your eye or if you think you might damage your eye, contact your Optometrist to arrange an appointment to help.