I am most definitely NOT a doctor, but I can let you know a couple of things that helped me when I was consistently under the weather. Always check with your physician, but I don't believe these would be harmful to very many people.
First off, try to get at least some exercise and fresh air every day, even if it is just a leisurely walk around the block (or roll, if you happen to be chair-bound). Being outside is in many cases better than being inside . . . even in large cities, the air contaminants INSIDE the home can be worse than OUTSIDE because of cleaners, pesticides, paint, building materials, mold, etc. If a daily walk isn't possible due to crime or it truly is just too dirty in your area for your health, try to make it to a public garden or park once a week and spend some time outside.
Drink plenty of water. Cutting out sodas and flavored drinks and replacing it with a glass of water is SO much better for your health. If you find that you don't drink much during the day, make it a habit to take a drink of water before every meal, and with your meal. Keep a refillable water container with you at all times. Lack of water - and I do mean water, NOT just fluids - can contribute to bad digestion, headaches, sleeping problems, and general feelings of ill health.
Cut out smoked foods, such as smoked fish, cheeses, and the like. These can cause migraines in many people, and especially in people on several varieties of medications. Replace these with non-smoked varieties.
Use natural sweeteners instead of processed sugars in your cooking. In baking you can often substitute juices for water and sugar; many websites can help you in making conversions. And don't forget the virtues of honey, which the Prophet (saw) said could cure any ills!
And don't forget to regularly check your cabinets to make sure that your food is halal . . . just today I learned that one of my favorite chip (I guess you would say crisp) manufacturers was now using pork fat to add flavor to their "all natural and healthy" chips, instead of just baking them as they originally had!
Allah keep you in His grace, and be thankful for His challenges in this life, for the rewards in Jannah will be great, Allah knows best!