Q: iMessage sending My ID as email instead of phone number

I've been texting someone through Imeessage, and for a while, when they received my messages, it would show my phone number. Now, my ID comes up as my email address. I tried going onto the message settings, and tried selecting my phone number on the "Send & Receive" option. I tried removing the email, but it won't allow me to remove the email. Any ideas what is going on and how to fix it.