Fresh pure wheatgrass juice is an INTENSE detoxifier, and as such I (personally) would never-ever do a wheat-grass juice fast until after I'd done some intense colon/liver/kidney cleansing, and had experience with juice fasting.
Do what you'd like, but the last time I recall actually following 'where you are and what all you've done', I recall parasites being a concern - and I don't recall ever reading about your parasite cleansing experiences. (of course, you maybe have posted elsewhere or not posted about it at all - I'm only mentioning it because if I had parasite issues, I would definitely attend to those before I'd consider using wheat juice for anything but nutritional purposes).