It is likely that this was a reaction to the Xanax. If this has not been prescribed to you by your doctor, do NOT take any more. A lot of medicines purchased over the internet are not always what they say, and also can contain potentially dangerous substances.
Gatorade is a sports drink and apart from a lot of sugar, I do not know what other nutritional value it has.
Make sure that you eat sensibly - a proper nutritional and well balanced diet that consists of fresh fruit and vegetables and lots of water. Getting dehydrated can also cause dizziness.
You can still lose weight by eating healthily without calorie counting and by making good choices of food to eat. For example boiled potatoes instead of fries; a piece of fruit instead of a chocolate bar. Also reducing your portion sizes will help too. Any form of exercise will help with weight loss even if you just go for a short walk every day and as you build up your stamina you can go for a longer and faster walk.
Losing 1-2 pounds a week is a healthy way of losing weight. If you do starve yourself, you will only put it all back on quickly once you start to eat like you used to.
There is a lot of free healthy recipes on the web to help you make some changes to your diet to help you lose weight.
The important thing is every diet will work, if you stick at it. You can have a piece of chocolate, wine, etc., but this need to be eaten in moderation.
Check the side affects of the Xanax, it sure could be that. It could also be the lack of protein. Peanut butter is a good cure for that, and it sounds like it worked.