Tracey
Hi Yael...so, yes, you can absolutely add b&p drinks to your fast!
Now...I haven't heard of the psyllium seed/flax seed etc product you're using, so I don't know if it will produce the same results as the plain old psyllium HUSK. (psyllium seeds are *much* different - it's the husk that does all the absorbing)
So, if the produce really does have psyllium SEED instead of husk, it's not the right product! (although I'm sure it's good for something!)
And, flax seeds are excellent for you...but they don't absorb and do what the psyllium husk does either...hmmmmmm!
Also...because you've got excellent bm's happening already, make sure you start out slowly with the b&p drinks...one a day for a couple days to make sure all is well in that department...
Hope that answers some of your questions....?
T