I have been having a lot of heartburn and feeling nausated, with light headaches. This has been going on for at least 3weeks what could be the problem?
I'm not a doctor and can't give you a diagnosis over the internet even if I were. By the title of your question you seem concerned about pregnancy. To rule that out, you can take a home pregnancy test when your normal period is more than a week late, or you can be tested by a doctor.
I wish I could figure out what it is bothering you and help, but I just can't. Perhaps someone else will try. Three weeks seems kind of long for it to be a routine virus infection, so you may want to see your family doctor about these symptoms.
If you end up finding out that you have acid reflux, you might check out these articles:
Enjoying Summer Despite Acid Reflux
10 Foods to Avoid with Acid Reflux
5 Drinks to Avoid with Acid Reflux