Issue sending Text from Macbook Air

ok, when I am work it is easy to send and receive sms messages from my phone and mac air. all of a sudden my mac air sends the message from my email instead of my cell phone. I have searched the FAQ and did everything i was told to do, signed out and back, made sure my number was listed on my account, etc....nothing is working...any more help? I have screen shots showing my cell phone is registered to my apple ID but when i click Messages on my mac air - Messages - Preferences - Accounts -Start new conversations from - Shows three emails and not my cell phone number.

when i go into my iTunes account it shows i can be reached at my cell phone number first, then the three emails that are listed. I have reset everything on my cell phone, and made sure my cell phone is listed everywhere.

Help!