You may have low blood sugar or be one of those lucky people who has a high metabolism. You may just need to eat smaller high quality meals numerous times a day. But most important, go to your Doctor and get a full physical. Better safe than sorry!
Pregnancy is just one of many causes of nausea. There are many reasons to your nausea, such as a digestive disorders, neurological disorders, allergic reactions to allergens, etc. You should see a doctor to rule out anything serious.
I suffered from nausea for years. The only remedy that helped was taking a prescription medicine called Doxepin. It's usually prescribed for migraines or depression but it worked terrifically to relieve the nausea.