Everyone has made great suggestions, but it's important to increase your water intake at the same time as taking fibre.
If you just load up on fibre with no water, you will have a large dry stool and will probably be just as constipated as you were when you were just eating meat.
Fibre soaks up the water in your intestines and creates large soft stools which move quickly through your bowels.
To blow out your colon, buy a large bottle of prune juice. Mix it with Psyllium Husk and some oil of your choice (Fish, Flaxseed or Olive would be good).
Wash it down with 2 Coloxyl and then shove 2 glycerin suppositories up your arse.
Within 30 minutes you will need to call the police because you will have killed your toilet bowl.
And like others have advised, start eating your fruit and veg again.