my mac is sending out imessages not using my phone #

What is listed on that pane under You can be reached for messages at?

F only your Apple ID then that means your phone is not linked to messages. To resolve see:

Select the email addresses and phone numbers that other people can use to send you messages. You can update this list on the Apple ID account website. See the Apple Support article Add or remove your phone number in Messages or FaceTime.

hello! i am having the same issues and tried what you suggested but i dont have the option to use my phone number on my mac, only my apple ID is listed and i cannot uncheck it. anyone else relate to this?

If you go to Messages>Preferences>iMessages what is listed under start new conversation from?

You can change what is listed.