@anamur-- Morning nausea is not a good way to predict pregnancy at all. There are so many possible causes of nausea other than pregnancy and there are plenty of women who don't experience nausea during their pregnancy.
Many different gastrointestinal problems can cause nausea in the morning. If you also have stomach cramps, vomiting and diarrhea, these all point to a problem in the stomach and/or colon.
Medications can also cause nausea in the morning, especially if you take them at night or first thing in the morning. Check side effects if you're on any medications.