Do I wear my N95 mask over my niqab or under my niqab? What about my burqa? Does that count as a facemask?

The niqab doesn't count as a face mask since the cloth of the niqab is quite thin, it wouldn't protect you from the virus. Covid-19 can also spread through clothes so it's important to wear the N95 mask whether you wear it under the niqab or over the niqab. I'd suggest that you wear the mask over the niqab so that the virus doesn't come on your niqab. Be careful, wash your hands every now and then and sanitize them. Most importantly try your best to stay at home as much as possible.