it says I can't have more than 5 devices authorized but I only have my phone on my account and I'm trying to authorize my Mac

The limit of 5 is for computers; the phone doesn't count. Try deauthorizing all as described below in Authorize or deauthorize your computer for iTunes Store purchases - Apple Support

Note that the Deauthorize All button is shown in the second screenshot below

1. On a Mac, open the Music app, Apple TV app, or Apple Books app. On a PC, open iTunes for Windows.
2. Sign in with your Apple ID.
3. In the menu bar on your Mac or PC, choose Account > View My Account.

1. 
2. Sign in with your Apple ID.
3. On the Account Information page, scroll to the Apple ID Summary section. You'll see the number of computers that you've authorized with your Apple ID. You can’t see the names of those computers. If you haven't authorized 2 or more computers, you won't see this section.
4. 
   
5. 

If the number of authorized computers listed is more than what you expect, you might not have deauthorized the computers that you no longer use, gave away, or sold. You need to deauthorize all of your

computers and then authorize each one that you still use.