My iMessage is on but messages are sending as sms

Okay, next thing to ask, are you able to send an iMessage to anyone else? If yes, then it is an issue with the other person. If no, then try turning iMessage off, power cycle your iPhone, then turn iMessage back on again. Understand, for iMessage to work correctly, both the sender and the receiver have to have iMessage activated, and both have to have an active connection to the internet. If one of those things is not present, it won't send as an iMessage.

Don't forget that iMessage is only between iOS devices. Go to Settings>Messages>and make sure that iMessage is turned on. If it is, make sure there is no error message beneath it, such as "Waiting for Activation".