Is it possible to not know youre 3 months pregnant?

Absolutely. Many women have irregular periods which makes it more difficult to determine when you are late. This can be caused by many things including a change in Birth Control. Some women produce what seems like a normal period even after they are pregnant. Its also possible for women to produce false negative results for a few months at the beginning of a pregnancy. There are many varying factors that could cause a woman to not know she is pregnant for a few months.