College girls especially don't know there pregnant until the second trimester because they have no symptoms or they come and go and they think nothing of it. And this is prefectly fine and happens to alot of women. Not everyone vomits everyday or shows symptoms we are all different.
Pregnancy symptoms are unpredictable. They change for time of day, activity levels, what you are eating. If you can figure out what makes them worse, you can avoid it.
Yes, pregnancy symptoms do fluctuate. Every woman experiences different pregnancy symptoms, while some women never experience any. Additionally, women may feel different during each of their pregnancies. Common symptoms include fatigue, breast tenderness, and morning sickness.