Sounds to me like you have Reactive Hypoglycemia (RH). The best place to discuss this is "upstairs" one level in the Diabetes forum. There are already some active threads on this condition. I will gladly meet you there to help as I have lots of experience with this condition.
Here is the down and dirty on RH...
RH is a precursor to diabetes - a chronic metabolic disorder that is often not recognized or treated by the medical community. Unless you have a doctor who is nutritionally savvy or has a more holistic approach to health, you will likley not get treatment from a medical doctor.
Reactive Hypoglycemia is caused by a completely imbalanced metabolism. In simple terms, your body overproduces insulin in response to elevated blood glucose levels, and when your blood glucose bottoms out, your body overproduces cortisol in an effort to raise the blood glucose levels back up. The excess insulin causes shakiness, lightheadedness, dizziness, passing out, numbness and tingling, etc... and the excess cortisol can cause stress, anxiety, and often, panic symptoms.
RH typically occurs in the twentysomething age group and is brought about by poor eating habits. This could be a combination of eating carb-heavy foods, high fat meals, lots of sugar (even from fruit), fast food, etc, or from keeping a really bad meal schedule (skipping meals or working out on empty). College students and those who recently moved out on their own are at risk because the eating habits tend to be poor. But ANYONE can get this and it does take a bit opf focus and discipline to recover.
There is no medication that will cure RH - but you can overcome it if you make some lifestyle changes. The primary goal in a treatment plan is to rebalance the metabolism. Here are important steps to take NOW that will provide immediate relief:
1. Eat a small meal or snack EVERY 2 hours, regardless if you are hungry, starting when you awaken in the morning and continuing until bedtime. After you stabilize you will be able to eat every 3 hours, but you need to first gain control. This meal/snack must contain a combination of carbs and protein - preferably from high quality foods. Make sure your protein levels are adequate - about 30% of total calorie consumption with every meal/snack.
2. Eliminate ALL junk food and for now omit all bread (rolls, croissant, muffins, cakes, pastry, cookies, etc), pasta, potatoes, and all sugar products. Your carbs should consist of fresh vegetables, low-sugar fruits (apple, strawberry, blueberry - but not orange, banana, grape), beans, nuts, seeds, soy, brown rice, and whole grains (but not bread - for example triscuits or shredded wheat cereal are okay)
3. Do NOT drink juice or soda of any kind.
4. For now, skip the protein shakes for several reasons. Get your nutrients from real whole fresh foods. Drinking calories can cause the glucose levels to spike - you need to avoid this. There also may be ingredients in there that are causing you glucose to spike and plummet.
5. Make sure that you have a meal or snack 30-60 minutes before you excercise. Have a snack with you at all times and keep it handy during excercise (in your pocket if possible). If you feel like you are going to pass out, eat your carb/protein snack immediately, drink at least 12 oz of water, and do not resume excercise until 30-45 minutes has passed.
6. Make sure you are eating enough calories spread out evenly throughout the day. In other words, you can't eat 200 calories for breakfast and lunch and then 1000 calories for dinner!
7. Stay well hydrated. Drink pure water where ever possible.
It is possible that you do not have RH and that something else is wrong, but your symptoms, as you describe them, are "textbook RH." In any case, applying the abopve strategies will not hurt you in any way if it turns out to be another problem, so there is no risk in trying to see if this works. Results will not be immediate, and there are other important things to understand, but I will not get into that here.
Good luck, and meet me "upstairs" if you want further discussion on RH