I think suzi-q has given you the very best possible advice! You need to get to your doc and have a really thorough check up. Feeling dizzy for three years is not good. I don't want to scare you, it could be a million simple things like a vitamin deficiency, something to do with a hormonal imbalance since you say this happens on a monthly basis, you could need glasses or a new prescription if you already wear them..........like I said, there are many simple explanations for what you are feeling. But you have spent too much of your young life already worrying about all the "what ifs......" It's time to get some answers and get on with enjoying your life.
I know you said that "no one knows what this is......." but there IS someone out there who does. You just gotta keep looking until you find them. Please don't give up! And know that we are always here for you, OK?
Peace
Greenlydia
You can definitely be suffering from anxiety. The light-headedness, the loss of appetite, the racing heart are all symptoms. However, before you chuck it up to anxiety, you should have a complete physical to rule out all medical conditions first. You also say that you feel it more during the middle of the month..is this during your menstruation? Heightened anxiety during this time is possible also. (Me, for example!).