air bubbles under paint????

my car is a 98 and is very well cared for. i wash and wax it all the time, but recently when i was going over it, i noticed some areas that look almost like an air bubble under the paint. when u rub the area it moves, and the last time i was washing the car some of the paint flew off when water hit it on the back bumper. beneth the white paint that flew off is what looks like ugly dirty white paint. what could cause this??? is it probally only on the plastic body parts where this could happen, or could it happen on the metal parts as well? also, if i was looking to paint one day down the road, is there any problem with having a white car, and painting it black? any help is appreciated, thanks!!