There can be a numbing , an almost "disconnected" effect. It can be in part due to the extra blood in the penis combined with a sub par libido.
I also found certain substances give me "numb dick." Among them...
Tribulus
DIM
Clomid
(All of these could be from extra estrogen).
On the other hand, Cndium (an ingredient in POST CYCLE) as well as NO2 (included in BIG BLAST) gives a nice boost to "hardonicity" without the numbness. Not sure why though.