One of the best pieces of advise I can give you, is for you to start a Food Diary.  You don't have to do this every day, for the rest of your life, just until your blood levels are sorted and you know which foods affect you and which don't.

Buy yourself a cheap notebook and write down everything that you drink (including water) and eat (including snacks).  Write down the quantities and the time at which you ate or drank.  Also write down how you felt directly after the food and a couple of hours after the food (did you feel grumpy, tired, exhilarated, do your joints ache, did you have a headache, etc).  Write down how you feel when you first get up in the morning.

As your diary progresses you will start to notice patterns of feeling ill or feeling well.  Examine what you have eaten prior to feeling ill or feeling well.  Notice how different foods affect your blood sugar levels.  You might find that certain foods or certain combinations of foods sends your blood soaring.  For instance, I found that potatoes sent my blood reading up dramatically.  I solved this problem by cutting out ordinary potatoes and substituting sweet potatoes.  Sweet potatoes are widely available at all major supermarkets.  They have much more flavour than ordinary potatoes and are absolutely delicious cooked in their jackets in the oven, they are also delicious raw.  I also found that tea and coffee sent my blood levels soaring.  I now use a coffee substitute, called Barley Cup, that is available at all health food shops.  There are several coffee substitutes but ensure that you check the ingredients as some add lactose (milk sugar),  and it will send your blood readings up.  Get into the habit of reading the labels of every single thing that you buy, don't assume that you have bought it once and it was OK, so it will always be OK.  Companies have a very annoying habit of changing the ingredients and slipping sugar or other noxious substances in.

Pay attention to how you feel.  If you get indigestion don't just pop an indigestion tablet in your mouth and carry on eating in the same way.  Look at what you have eaten and work out what gave you indigestion.  Did you over eat or is it a certain food that doesn't agree with you?  Or perhaps a combination of foods?  Do you feel bloated and uncomfortable after eating certain foods?  It is amazing how many people have allergies to foods but just don't realize it.  A food diary will help find any allergies.  When my wife was young she had eczema, sinus problems, catarrh and loads of sore throats.  For ethical reasons she gave up dairy products and low and behold, no more eczema, sinus problems, catarrh, or sore throats.  Years of suffering that could have been solved just by cutting out one food product.

You might find that you can eat some foods raw but they cause unpleasant symptoms when cooked.  My wife can eat muesli with cold soya milk but with hot soya milk if gives her indigestion.  Experiment and see what suits you.