does anyone know or practice pal dan gum qigong.

I've recently started "Pal Dan Gum" from a book I bought from amazon.

On my 3rd day of practicing it and it has truly brought some great effects in energy...well I guess all Qigong techniques do, but I'm new to it.

I've started practicing Pal Dan Gum a month ago, everyday. I feel good but I really don't know if it is about energy or only because of the result of a good breathing and concentration. Certainly, I know I will feel that energy but, for the moment, I can't. Can anyone give me any advice to feel that energy? Maybe, I just have to be patient, haven't I?
I also practice yoga so I have some knowledge, but yoga doesn't work with energy like Qi gong.