Hello Marina,
I think one of the things you've got right is your attitude - wanting to sort it out. It takes time to find out what suits your body. I, for example can hardly tolerate any fruit but chocolate (not chocolates), surprisingly, hardly bothers me (although I do have problems after the first hundredweight). This, however, relates to something that has not been mentioned specifically - GI (Glycemic Index) low or high. This is quite sound and not a fad. Foods with a low GI take longer to digest and absorb and high GI quickly gets into your system - including the sugar(s). Steve Redgrave (amongst others) got his diabetes sorted by following this diet. There are plenty of books about it and you could Google it to get more information.
Good luck,
Russ