Well you cant feel the liquid because much of sexual pleasure for a female comes from the actual "pressure" and not the "tickling" feeling of something in there. We can wear super large tampons and never feel them after they are put in. Mainly because there are not little nerves on the surface of the vaginal walls.
Gspot is not sensitive unless "pressed on" often times very aggressively pushed into, the cul de sac or fornix isnt sensitive to the touch as much as to aggressive thrusting.
Our labia (inner and outer) is sensitive to the touch (as well as the clitoris obviously) because the nerves are on the surface much like our skin. But the tissue inside of the vagina is not made that way.
You can lightly touch your own cervix with your finger and not really feel it unless its tapped hard or scraped with a fingernail for example. So feeling a little bit of warm fluid isnt going to be noticable, especially after a hard fucking. At best if a guy is a very very hard ejaculator you might feel a little something.
Now when it runs down your leg, thats a whole different sensation.
