You need to eat more calories per day. You should be at least at 2000 a day for male. Starving is not good for you as you cannot get nutrients to repair yourself. Get some breakfast steaks, or chicken breasts to bake or broil, and frozen veggies.
Birdseye makes several nice simple mixtures, without sauces (which may have MSG in them), for you to start with.

Your goal now is just to find your trigger. Usually PNers find that something in their daily life has pushed them into this malady.
Something they do (like straining themselves with too much or too many extreme forms of exercise), exposure to toxins in solvents or the air, too many vaccines, viral and/or bacterial infections, alcohol, diabetes, kidney disease, hepatitis, food allergies or intolerances, thyroid derangements, ---there are so many possibilities.

Right now it is not difficult to find foods. You can eat in moderation (unless you find yourself gluten intolerant) some breads. Starving yourself for some "diet" seems too radical for a beginner. You can start by eating 1/2 the bread you would normally eat. Then pare that down week by week as you get used to less.

Keeping a journal would be helpful as you can look back to what you ate yesterday and the day before to track your symptoms or improvements. Pace yourself, and make changes over the next weeks. It is too difficult to jump in and try to make sense of what will work for you.

This link may help you alot. I have this book, and found it very sensible and intriguing.
http://obesitysanswer.com/

While it targets overweight people, it explains how food intolerances make you sick, make you overweight and unhealthy. It explains the food groups that are the biggest culprits. example: The Lily Family (onions and garlic), The Nightshades (all peppers --hot and not--, paprika, tomatoes, potatoes, eggplant)
Dairy, gluten, chocolate are the most common to try eliminating one by one (and reintroducing), to see if they disagree with you.

Over time people can discover what bothers them and fix that.
I bought my copy years ago at Amazon...it is a trade paperback and not expensive. Sometimes you can use the used book feature and save alot of money on Amazon.