I was also wondering if you have/ had had any sort of ED/ disordered eating patterns. If you have then writing about them of in a PM to me could help.
Eating a lot and that causing you to feel or even be sick is quite normal so that does not surprise me. Sometimes pain can make you lightheaded and eating high fat/ protein foods can make you feel hot and sweaty if eaten in large amounts. Have you noticed any patten between the type of food you wag and this occurring? There is a chance it could be some kind of intolerance to it.
Is your neck always affected or just some of the time? One thing I did wonder I'd whether it was your blood pressure going up but it would have to be extremely high to notice. Another thing I was wondering about is stress or anxiety causing this and you don't necessarily need to feel panicky or anything.
Really it is something I am unsure about and as it's happening often, by the sounds of it, I would advise you see a doctor and, in the meantime keep a diary of EVERYTHING you eat (a food diary, there may be examples of this on the net if you're unsure) and then add to that if you get any symptoms and what. It is important you put everything you eat so any patterns may be seen as it may not be as straight forward as you set x and it starts after that. It may also be worthwhile putting an idea of the quantities of it you eat too in your case.
Sorry it doesn't really give you an answer