How to self-remediate mold?
A question - were there elevated spore levels in the rest of the house? It sounds like you disturbed something removing the old drywall. If that's the case you might be OK.

You need to identify the source. Once you've done that you can usually deal with the problem yourself.

The hard part is going to be identifying the source. Mould is usually caused by condensation on the walls, which in turn is caused by poor ventilation and insulation. So there's warm, damp air in the room which when it comes in contact with the cold wall forms condensation.

If there was no visible mould before removing the drywall, then you should be all right - but I'm not an expert so please don't quote me on that.

When you replace the drywall make sure you install adequate insulation and ventilation in the room and then perhaps test again for spores before decorating. If the levels are still high then you'll need to do more investigation.