Here is some input and advice from FAQ Farmers on the subject:
The exact causes of phantom pregnancy are actually still unknown. It is thought that it is simply the body tricking a person into thinking that they are pregnant.
Either being desperate to be pregnant and being unable to get pregnant, or having had sex and being really guilty about it.
A phantom pregnancy is when a woman thinks she is pregnant, though all tests are negative and possess all pregnancy symptoms ( swollen/tender breasts, frequent urination, weight gain, nausea, etc.). Basically they full their body into thinking it is pregnant. Some women will have a phantom pregnancy for up to seven months and even admit to feeling the "baby" kick, even though nothing is really there.
nope, it happens often...
yes because to have the phantom pregnancy your body secretes pregnancy hormones which is what pregnancy tests look for
Yes. In a phantom pregnancy, the body is tricked into feeling like it is pregnant. Consequently the same hormones present in a real pregnancy will be present in the body of someone who is undergoing a phantom pregnancy, and these hormones are what a pregnancy test detects.
You die
IF YOU ARE SURE they are all girls then one is probably having a phantom or false pregnancy.
Nausea during pregnancy is caused by changes in the hormone levels in the body during the early stages of pregnancy. It usually happens early on in the pregnancy.
A horse who is experiencing a phantom pregnancy will have symptoms of an actual pregnancy. These symptoms include the horse being tired with a puffed up stomach.
Yes
Yes; it is called a phantom pregnancy. Which basically means that it is all psychological. Either you are very afraid, guilty, paranoid etc. about being pregnant that you think your mind into being pregnant or you want to be pregnant to bad that you fool your body into thinking that you are pregnant. You will experience pregnancy symptoms and can even lactate during a phantom pregnancy.
NOTHING
Nothing
The only difference between a phantom pregnancy and a real pregnancy is that with a phantom pregnancy you are not actually carrying a baby and you will usually have a period and a negative pregnancy test. You will have the same symptoms as a regular pregnancy and they can last at least as long as 7 months.Scroll down to related links and look at "False pregnancy - Wikipedia"