Many things can cause that!
Here is an incomplete list:
1) anxiety, like mentioned above (as you mentioned stress)
2) hypoglycemia (where your blood sugar level drops when you haven't eaten for a while) (you mentioned this was associated with not having eaten)
3) pregnancy (you mentioned feeling nauseous, drained and tired - all very common in the first trimester)
4) low blood pressure - if you don't drink enough fluids, your blood pressure can run low, and certain situations, such as upon standing, can make you lightheaded or pass out
5) heart arrhythmia - this would be very unlikely, especially given your age, but still is a remote possibility
6) malnutrition - certain vitamin deficiencies can cause that; make sure you are eating a balanced diet and consider taking a multivitamin
But if I had guess, my #1 guess would be pregnancy.
Hi Kay, I would normally worry about an actual physical cause to your symptoms, but, since you mention stress along with physical symptoms that are associated with generalized anxiety disorder and even panic attacks, you may want to do some research on the aforementioned. An inability to handle stress and cope can really actually ruin a person's quality of life.
I don't know what is causing your stress, so I don't want to make light of it. I do know there are a lot of situations people blow out of proportion in their own minds, so be sure not to be letting yourself 'sweat the small stuff' as they say. In reference to more serious problems, you need to find a way to cope on your own or get some type of help with doing so...whether it be a family member, friend, church member, or professional counseling. You might be surprised how much getting things off your chest and knowing how others handle the same problems can help you feel better while learning new ways to think of things and cope.
If you do this and your symptoms don't get better, I would see a regular doctor. You may have a blood pressure/hormonal issue.
p.s. be sure to be eating healthfully (lots of whole grains, fresh*organic*fruits and vegetables, beans, and low amounts fattening foods) along with making sure you get adequate if not extra sleep. A good night's sleep makes everything seem easier. Tired people don't handle stress well!