Calculating number of nonzero elements in any symbolic matrix

ClearAll(p, d)
Format(p(a_, b_)) := Subscript(p, Row@{a, b})
d = 2
p(a_, a_) := 0;
p(a_, b_) := -p(b, a) /; (a > b)
pMat = Array(p, {2*d, 2*d})
MatrixForm(pMat)
Length(Select(tMat, # != 0 &))

How to calculate number of nonzero elements in any symbolic matrix. I have given an example of one symbolic matrix p above.