I wouldn't consider it exactly okay to eat that much every day, and it definitely isn't too healthy not to eat enough. You need food for bodily function, etc, but if you don't feel like eating then cramming yourself full of it isn't exactly too great either. For a few years I never really ate too much, and I often would just end up going to school, having perhaps a biscuit or half a sandwich, perhaps a drink, then that would be it for the day. From being quite a large child I went to being quite a skinny teenager, and I still am quite skinny to some degree.
If it is a considerable amount of nausea, it may come from not eating anything, but that is only an idea. You may feel lightheaded from not eating enough, and that does sometimes still happen to me even though I've picked up on my diet (a little). If I were you, I would definitely try to eat a little bit more, perhaps some light snacks throughout the day or a light supper before going to bed. Heck, people say breakfast is the most important of the day (I don't buy it) but you could try having a little fruit bar or perhaps an apple in the morning!