Hi Jen B,
Thank you for joining the Bose Portable PA Community. Welcome.
Feedback is never good. If it occurs in certain areas of the room, it's because in those areas, the sound from the S1 Pro is louder than it is from your voice, or you are standing in a way that the microphone is aimed at the S1 Pro.
Here's an article that explains the concepts.
You won't be able to do everything in the article because you have head worn microphone. Make sure the microphone is positioned close to your mouth. This may allow you to get the same loudness without having to turn up the S1 Pro so high.
Please give us a link to the owners manual for the head worn microphone. I'd like to understand what we're dealing with.
How large is the room (dimensions please)?
How many people are in the room?
What are people doing when you are performing?