Using the Digitech Jamman Looper live- why does it feedback?

[Denise Lauren Dill]

I recently played my first few songs live using the Digitech Jamman Loop Pedal. I had a mic and my electric guitar plugged into the pedal and then had the pedal plugged into the board. With each loop/layer I added while playing live, the worse the feedback got. I'm assuming part of this was because the mic I was using to record some loop parts started picking up the live sound from the PA. Is that it? Is there anything I can do to get a better sound and avoid feedback like:

Tricks to setting levels on the pedal in relation to the board
Special mics to use
Positioning on stage
Adding a preamp

If anyone has any answers or knows where I might go to find answers I would so appreciate it!!!!

Thanks,
Denise