If you suspect a mold problem in your home, the best thing you can do is to contact a professional and get it checked it out. Not all black spots on walls are mold.
A certified mold inspector will be able to come in and take an air quality test or surface sample, look for other signs of mold contamination, and identify the cause of the problem (usually some form of moisture intrusion). You might have a leaky pipe behind your wall, cracked foundation that’s allowing water to enter your home, or you might simply have a spider infestation.
Remember, if it is mold, the longer you wait, the worse the problem will get. A professional mold inspection will give you the answers you need to address the problem quickly and effectively.