The problem you are having is that you have been listening to the wrong people for advice. Doctors have NO training in nutrition and do NOT understand how the body works in regard to nutrition. Depression is commonly diagnosed by these guys when they can't figure out a medical reason for your problems. Another one is "autoimmune" disease or one of the best is "chronic fatigue syndrome."
The reason you feel better when you drink stimulants is that your adrenal glands are most likely exhausted. This is due to a bad diet high in carbohydrates, low in fat, low in complete proteins. Many vegetarians suffer from this problem.
The first thing is to get hydrated.
Take your total body weight and divide by 2. That number is the amount of water in ounces that you need to drink each and everyday. Along with that, you should consume 1/4 teaspoon of "air dried sea salt" in conjunction with each quart of water you drink. This puts the electrolytes in your body that will give you proper hydration. The typical white table salt you buy in stores like the Morton Salt, for instance, is terrible for you and has loads of chemicals added. Avoid that junk. If you drink ANY diuretic drinks like, sodas, coffee, tea, alcohol, commercially prepared fruit drinks, energy drinks, etc., these all dehydrate you and you will need to add more water to the total to compensate for the water loss due to these diuretic drinks. Take the total ounces of the diuretic drinks and multiply by 1.5 and add that total to the original total to come up with the proper amount of water you need to drink each day.
Many times just getting hydrated will greatly help your situation.
I suggest you get a book called, "Life Without Bread" by Christian Allan, Ph.D. This book will give you some basic incites into how you can manage your weight, etc. and remain healthy doing it.
Energy drinks are very destructive to the body and cause long term health damage. Red Bull and others have been banned from several countries now due to causing many deaths.
The "make believe energy" you get from that junk is due to the excess cortisol being produced by your adrenal glands that become exhausted from drinking that junk. Cortisol is a stress hormone and is part of the process these drinks that cause your body to assume it is under great stress. This reprioritizes your liver and other organs, causing many changes in the way the body makes hormones, etc. It is just NOT something you want to do.
To address your basic problems, you should see a Certified Nutritional Therapist that can help you become truly healthy; not that "make believe health" being promoted by doctors prescribing drugs to treat symptoms and not "root causes" of disease.
good luck to you
CNT, B.A. biology & chemistry
Advanced nutritional research