Are you eating enough calories and carbohydrates? www.***********.com is a free website that will help you with your meal plans.
Do you know what your iron levels are like? You might be anemic which can cause the lightheadedness and headaches and such. Also if you are on hormonal contraception it can cause some similar symptoms so talk to your doctor or a contraception nurse and discuss whether that is it. It could also be symptoms of Chronic fatigue syndrome (which I suffer from) which is normally diagnosed after adding up many symptoms and ruling other things out or it could be a simple bug. The best way to know is to ask the doctor to run a few simple blood tests. It could also be food allergies. I'm sorry if that's not very specific but I hope it helped in some small way
All I can say is that it sounds strangely like what I have experienced in the past few months but can't get any answers...All I get is doctors looking at me like I'm making it all up....I hope you get some answers