Depending on the kind if head, and how you hit it, the rolling tire can tip a nail up causing a puncture to itself. Ot the nail may not be laying flat, or it gets stuck to the tire, goes once around and enters the next time around. (or your ex-girlfriend has it in for you).

The how doesn't matter, except as a matter of intellectual curiosity. What matters is that you got flats, plain and simple. They could be flukes, or a reflection of where you ride, like past a construction area.

The sealant will probably help slow the leak while the nil is still there, but often pulling it makes things worse. With sealant, it'll depend on how big a nail, with the sealant plugging a thumbtack hole, but not a larger nail's.