Firstly, congrats on your first post and welcome to PC!

You mentioned that you have a lot of acid coming up into your stomach, have you or your doctors ever looked into acid reflux disease? I have that and the burning can be unbearable sometimes no matter what I eat/don't eat.

700 calories a day is a bit low. Generally less than 1300-1500 is considered starvation (depending on your source). To me, the nutritional value in what you do eat can mean more than the food itself. In my opinion (and this is just me) as long as your bmi is within a healthy range and you as long as you still desire to eat and to be healthy then you are okay. Perhaps you should discuss your concern with your doctors?