Why does iMessage send my texts through my email?

Ever since updating to iOS7, my iMessage would not connect. I finally backed up my phone to my cmoputer and erased all the data on it. I then restored it and iMessage worked. Now I have the problem that its sending my messages only through my email. In the "iMessage -You can be reached by iMessage at" it shows my phone number and two emails. My emails at checked but it doesn't give me the option to check my number, it's simply greyed out. Someone please help. I never had trouble with this and it'd be annoying to texts all of my contacts through my email.