I used to get sick pretty often. Then I became a vegetarian (although organic meat plus ample fruits and veg would be the equivelant), became aware of all the chemicals in my home and found alternatives for 95% of them, started meditating regularly to reduce stress and started doing an annual 2-week detox fast on vegetable juice. I have been sick twice in 12-years since.
*edit: the meat thing is acutally important for your health because of the vast amounts of hormones, antibiotics and pesticides that are in meat (which aren't in a vegetarian diet), whcih will weaken your immune system. I don't know how accurate this is, but I have read that between 75% and 90% of the pesticides in the food supply are actually in meat, because they spray it onto the piles of grain that they feed the cattle to prevent insects from infesting it, then the cattle eat it, obviously. In addition, and there is no science to support this other than common sense, but consider the fear hormones that are released into the blood streams of the animals in the brutal way they are killed, that stuff will still be in the meat when you eat it, hypothetically. So when eating meat it is even more important than with fruit and veg that you eat organic as often as possible.