Holy shit- I cried.
If you have problems primarily with infections, then there may be a nutritional course of action that can be helpful. One problem with being born premature is an opportunity to fill your gut with the good bacteria necessary to supplement your immune system. I think... at any given point in time the average human has about 10-100 (it may be more like 10,000, I can't remember) good bacteria for every human cell on their body (we are mostly foreign critters O_O). Antibiotics are NOT trivial because they kill both. Necessary if an infection occurs, but afterwards it's necessary to get those good bacteria back because they help ensure that digestive resources get used effectively (necessary for proper immune function).
Whatever you do, don't go vegan or vegetarian. They aren't good ideas for people with health problems. As far as nutrition is concerned, you want easy energy that can't be absorbed by bad bacteria. That means eliminating sugar as much as possible. Not just 'sugar,' but naturally occuring mono and disaccharides (IE lactose from milk). If you can't eliminate, try to keep it to under 1 gram per serving. What you want are these things call oligosaccharides- they are short chain starches or complex sugars that will ferment in your gut, stabilizing your GI tract's Ph and feeding good bacteria as it gets broken down into simple sugar. Our primary source for the oligosaccharides necessary for building gut flora is in mother's milk- after that we don't find large quantities of it in average diets. Asparagus, garlic and Soybeans are good sources of the three types.
http://en.wikipedia.org/wiki/Inulin#Natural_sources_of_inulinhttp://en.wikipedia.org/wiki/Oligosaccharide#SourcesYou also need good bacteria. The easiest way to do this is by making your own Kefir. You just need a 16oz jar, kefir grains (you can get 'em freeze-dried online) and milk. The Kefir grains are yeast/bacteria cultures that eat the lactose. Just let them ferment at room temperature for 24 hours in a glass jar with milk. strain out the grains and drink the liquid. Reconstitute the same grains with milk and repeat. It's very easy and in 2 months you'll probably no longer need to use toilet paper (in a good way). I like recommending kefir because it's incredibly inexpensive and it's an easy solution to keep up with. If you did only one thing, this would probably help quite a bit. Kefir will still have lactose in it (contradicting the point above), but it's going down with lots of good bacteria.
This obnoxiously awful website pretty much started the 'Kefir revolution'- it's a good resource but there may be more succinct sources elsewhere
http://users.sa.chariot.net.au/~dna/kefirpage.html.
Otherwise, try to stick to pickled and fermented foods. Truly picked foods, in the ingredients list, will have only salt, water, and the food being pickled (plus spices)- it won't have vinegar or any kind of sugar. On the nutritional facts, pickled food should also have a very low or nonexistent sugar content (less than one gram). Sauerkraut and pickles are the easiest things to find-- but if you feel like this sort of thing is helpful to you, making pickles is incredibly inexpensive. Salt, water, jars (you can reuse jars bought from the store- they all have pickling lids that will repop from the fermentation gases), and stuff to ferment- plus the internet for some guides.
Stick to sourdough for bread- don't need to shy too far away from beer, undistilled fermented beverages help fight infection (stick to original bottle fermentation)- if your liver can handle them in small quantities. Also highly recommend supplementing with Zinc- it will help your liver and other aspects of the immune system.
Mmm... Oh. Recommend high quality (care not cut) beef. A chuck roast, when prepared properly, will run you about 4 dollars a pound and taste like rib-eye. Bivalves are also good.
