You want to improve your immune system which is the reason of this infection than understand the reason it is weak is because of candida (yeast) overgrowth in your body. Your primary defense against this is your diet which I would recommend you change for the time being. You need to consume foods that will raise your pH level and cause the candida (yeast) to die off. For that you need to cut out all the following foods:
1. Avoid all junk foods (white sugar, white flour, soft (soda) drinks)
2. Avoid all sugars (even fruits)
3. Avoid all grains ( Barley, Corn, Millet, Oats, Rice, Wheat)
What you need to get is apple cider vinegar not regular store bought vinegar. Here is what you need to get which will cost you next to nothing:
4. Get a bottle of RAW apple cider vinegar and take 2 Tbs in the morning and 2 before you go to sleep.
5. For the first 7 days you will only eat RAW leafy green vegetables and other RAW vegetables. If you don’t like to eat vegetables than juice them. You can find tons of recipes online. Do this every time you get hungry.
6. Get probiotics. I would suggest Garden of Life Raw Probiotics. Their main function is to provide balance for less-desirable organisms (such as yeast)
7. Eat lots of leafy green vegetables whenever you are hungry.
By doing so you will see results much faster and feel much too. I can tell you this from personal experience that this will work. But it will require effort on your part.