My iphone 6 keeps asking for my apple id password?

Every time I try making a change on the phone like turning iMessage on or off and even to change settings for WiFi, or if I turn the phone off and then turn it on again, it asks for the apple ID password. Once I put that in, it tells me it is wrong. But it is the correct password for sure because I can log in to my apple ID from my computer. What can I do to fix this?