iMessage isn't letting me use my phone number on my MacBook

On my iMessage options for receiving and starting new messages it won't show my number at all. And when I try to add my number it doesn't give me the option to. And on my phone its set with my # but on my Mac it doesn't let me. I know I had this problem before but that was awhile back and I don't remember how I fixed it. Its using my Apple ID instead