Villians stats are 23/9/3.0 over 25 hands. We are both deep thanks to some maniac paying off our overpairs, which was the only hand I seen him showdown(KK). What should I do here? Is villian ever semi-bluffing or playing worse 2 pair this way?

Full Tilt No-Limit Hold'em, $0.50 BB (8 handed) - Full-Tilt Converter Tool from FlopTurnRiver.com

Hero (UTG+1) ($93)
MP1 ($96.35)
MP2 ($20)
CO ($48.25)
Button ($95)
SB ($121.10)
BB ($64.25)
UTG ($51.10)

Preflop: Hero is UTG+1 with A, K
1 fold, Hero bets $2, 4 folds, SB calls $1.75, 1 fold

Flop: ($4.50) Q, 4, K (2 players)
SB checks, Hero bets $3.50, SB calls $3.50

Turn: ($11.50) A (2 players)
SB checks, Hero bets $8, SB raises to $20, Hero?