Why won’t my iPhone 14 Pro use the microphone in my Bluetooth headphones even though it’s connected?

I’ve noticed that when I try to do videos, or I am sending them on apps to my friends, if I move away from the phone during recording in the playback, you can hear my voice get quieter like it is using the internal microphone on the phone. Not the microphone built into my Bluetooth headset, even though my Bluetooth headset is actively and properly connected. Is there a setting or a fix to this? It is very frustrating. I also have the current version 18.1.1 and am not in beta, thank you!