NightSky
Hey Night Sky, I think I figured out what's going on. In the Google Messages app, there's a way to input your phone number under the advance section. You'll have to clear the cache and app data, which will de-register you from RCS, then add your phone number to that section, then register for RCS.
This is left over from SMS texting as this way Google messages can determine Who you are in a group conversation and not create new ones.