Heard of this condition & agree with dkcx - u prob use too
much strength when u pcc. No matter how strong or tight the vagina
is, it can't compare with the grip of a human hand (& a male
one at that).
U could try masturbating with a 'light' hand - use less strength
lah..Let your dick get used to the feeling of less 'force' or
'grip'. Be gentler..
In the meantime, maybe u & yr gf could also try out
different positions? Different postitions - yr dick gets rubbed
different ways & it shd feel gd for yr gf as well.
Does she feel lousy that she's not getting sex? Be sensitive to
her feelings as well, yah..
Good luck!