Well masks are for when you are well, so that you have less likelihood of breathing in the virus (or bacteria)
Also, the masks are good for when you are sick and you go out to not cough anything on anybody.
But, when you are at home, and sick, the mask does no good. In fact, it inhibits airflow, and the coronavirus attacks the lungs really badly.
I actually read there is the possibility of masks making you sick as they can act as a sort of reservoir for the virus to replicate.
first, there are two types of masks
The folded flat masks are just for keeping your spittle off of other people.
They do not help for anything else.
The N-95 (keeps out 95% of particulate dust) can be a barrier to you breathing in viruses and bacteria. So, they are better protection than nothing.
However, over time, they get moist from your breath and can be a way of accumulating, and keeping alive the viruses you want to avoid.
Further, when you are most virulent, is just before you have any symptoms. That is when you should be wearing a mask to protect other people, but you don't know to do that.
When a person is sick and having trouble breathing because their lungs are filling up with mucus, a mask can kill them, just like putting a pillow over their face.