How one can know when he/she is sick from household mold?

Respiratory symptoms. Mold allergy triggers asthma and nasal symptoms in susceptible persons. Of course, many inhaled allergens trigger such symptoms. Suspect mold if there's a moisture problem in your home. Look for wet carpeting, water stains on ceilings & walls, condensation on or around windows, discoloration of shower curtain, tiles & grout & leaks around sinks & hot water heaters. See a board-certified allergist.
Mold allergy. I would see an allergist for testing since it might not necessarily be the mold causing your symptoms.