Other signs present? A woman of childbearing age who has some nausea (with or without vomiting), some fatigue (feels less energetic), a sharper/stronger sense of smell, mild soreness/swelling of her breasts, and maybe some food aversions and cravings . . . Could be pregnant. Symptoms can occur before missing a period. Diarrhea can occur coincidentally with pregnancy symptoms, but is not considered a sign of pregnancy.