Of course, stereotypically, pregnancy is the most commonly cited cause of nausea in the morning in young women. However, there are other possibilities as well.
The most likely is low blood sugar/ hunger. Even though you eat breakfast, it may be that your body wakes up so hungry that you are already nauseous. You could try having a snack at the bedside that you eat even before getting out of bed. Alternatively, you could make eating breakfast the first thing you do in the morning (before showering, dressing, etc).
Another possibility would be gastroesophageal reflux disease. This is a condition in which the muscle between the esophagus and stomach relaxes, allowing stomach acid to wash backwards into the esophagus and mouth. This causes heartburn symptoms, a sour taste in the mouth, and can also cause nausea. If you have any of these symptoms, this might be what is going on, and you might be able to fix this by taking an antacid medication, preferably in the night right when you lay down to prevent the acid backwash.
If these ideas do not make sense to you, then you should talk with your primary care doctor
to determine if there is any thing else going on.