My vp$ip is 20.35%, and pfr% is 4.35%.
I would have to assume you aren't raising preflop nearly enough.

According to your pfr percentage, you are only raising the top four percent which roughly means:

AA, KK, QQ, JJ, AK, and AQ.

This is hugely telling, and any aware player isn't going to be in the pot when you raising unless he has a stacking hand like a pair, or a dominating hand like QQ+, AK.

I am only marginally winning at 100nl, so take this for what its worth. I play fewer hands than you do but I raise almost twice as many.

Off the top of my head, my vpip is 14.5% and my pfr is about 7.5%.

Try raising more weak hands in position like JTs, 77-TT, ATs, QJs, the occasional 45s. Also try raising more hands overall. Expand your overall raising range to include AQ, KQ and AJ in MP or later, TT, and etc.

Hope that helps.