It depends on what mask it is and whether I'm going somewhere with questionable ventilation or crowds. If it's one of those accordion-folded blue paper masks, I'll always put a cloth one over it. A while ago, though, we found an old box of N95 masks in our barn. (They smell a bit mousy, but hadn't been actually peed on. lol) They have a really snug fit, and most of the time when I wear one of those, I don't double mask.
Again, though, it depends on where we're going. My son needs to get allergy shots every few weeks at the nurse treatment room of our HMO, which is big and has lots of people going in and out, many of whom are not well. After the shot, we're required to sit a half hour in the waiting room in case he doubles over with anaphylactic shock. When the pandemic began, they stopped treating walk-ins and only did allergy shots, which reduced the crowds. But now they're back to the full round, and lots of people are in the waiting room, sometimes coughing and hacking. I have to assume the ventilation is good, but do double-mask there, even when one mask is an N95. It's nerve-wracking to be forced to sit and wait with lots of other people, feeling exposed.
I've started double masking. I live in a really high covid area, and though I'm not going out and about much, I have been to some doctor appts, and like Annie said, sitting in those waiting rooms is nerve-wracking.
I'm also somewhat higher risk, so I just feel better for doing it, mentally.
I’ve worn two masks since the beginning of the pandemic before the CDC even recommended it. It was just common sense that double masking would be closer to filtration of a N95 mask
If you have a true N95 mask, and it fits well, you probably don't have any gain in double masking, though it can't hurt. I've been thinking about it, though I don't really get that close to people much of the time. So far, I haven't done so. I have a pretty thick cloth mask, but again, I have been thinking about it. Also been thinking of getting an N95 mask, as they say you can get one now. Peace.
In fact, with my N95 mask, I don't double up often because it makes it just that much harder to take a deep breath. So far, only for that endless half hour in the nurse treatment room waiting area with the coughing patients. Good luck with your Covid shot!