The porn may or may not be what is effecting your sex life. You need to get into couseling with him.

Of course with that said, you don't seem to be willing to compromise and allow him to watch porn, and you said you "confronted " him, so what do you expect, confront means you were already going from the view point it was wrong and bad.

It is possible that the drop in sex has other issues, but without communication no one will know.