Pregnancy can occur if you have had sexual intercourse. Around 85 percent of couples who have unprotected sex get pregnant within a year. There is a very small chance of getting pregnant while using contraception. For example, the contraceptive pill is known to be less effective if the woman taking it is also taking antibiotics.
Not everyone gets all the symptoms, some may only have one or two, and some symptoms could be attributable to illnesses.
If you are trying to start a family or suspect you may be pregnant, the symptoms of early pregnancy can be found by visiting this link