Phantom pregnacys are more common in animals, my cat had a phantom preg at one point, explains why I know so much about it.
The animal believes they are preg, for some reason something to do with chemicals in the brain, they then go to full term phantom preg. And then they have no baby/s and they carry on as normal.
Phantom preg. In humans, is usually from the person wanting to be preg. So bad that there body starts to beleive the mind, and then the symptons come.
Its all a case of mind over matter.
U can give your self a headache/bellyache/toothache etc if u think hard enough about it, and want it to be true.