Sounds like anxiety. I have the same issues with dizziness (lightheadedness) and nausea. If you suffer from HA, think about how your body responds to all that stress: tense muscles, physical and mental exhaustion, etc. This is enough to cause the dizziness (tight neck and shoulder muscles).
Again, I believe that we all suffer from the same symptoms. I get dizzy, nauseous, extreme muscle pains, shooting pains in my abdomen, and break out in sweats. Yes, I also think that I may have cancer, even after receiving the following treatments/procedures since February
1. Two ER visits -thought I was having a heart attack (sweats, chest pain)
2. Scope of sinuses (nose and throat)
3. CT of sinuses
6. Blood work (several times) to check liver and pancreas
7. Stress test Echo (heart)
8. Visit to a nueralogist (who told me to calm down and that I was a very health person)
9. Numerous vistis to my GP
After all of these tests, I have found that I have TMJD and non-erosive acid reflux (both non-life threatening issues). Yet every time I get nauseous, I think about cancer, gall bladder, etc. Like many on this site, I am forced to step back, calm myself down, and realize that I am just fine.