iphone 4s won't accept my apple id password for iMessage

for some reason my phone isn't sending iMessages all the time so i went to go back into settings and re-click the toggle switch on the iMessage hoping to "reset" it but for some reason the stupid phone keeps telling me my apple ID password is incorrect.

I just finally got the **** phone to accept the wifi password and now this all of a sudden?! why does this phone have such a hard time accepting passwords that are correct? i know the password is correct cause i just used it to log into this apple suport community!