At first all sorts of food will seem to be problematic. At first you need to mostly eat things that plug you up like white rice, white bread and potato (no skins) and simple white protein like eggs, fish and chicken *** - and drink fruit juice rather than eat fruit. You need to find a diet that gives you a manageable output. Then you can slowly introduce things. Other meats etc. You may never succeed with really high fibre foods but you will find you can slowly introduce things you like and eat a little WITH the white foods. Fibre on an empty stomach is not what you want! Plain potato crisps are better for you than celery now! Nuts may always be a problem but I found SMOOTH peanut butter is fine. You may need to forget what you were taught about fruit every day and 5 veggies etc. That was mainly for regularity and I promise you that will probably not be a problem. For vitamins, take a supplement and drink juice and slowly introduce the less fibrous fruits. Good Luck!