How often is this a bluff

[pho75]

Villian has been aggressive preflop and bets the flop almost always. He has been check raising out of position and taking down small and medium pots uncontested. He's been caught bluffing a few times. I have not been overly aggro pre and he should know I have a big pair or AK.

Ultimate Bet
No Limit Holdem Ring game
Blinds: $0.10./$0.25.
6 players
Converter

Stack sizes:
UTG: $27.05
UTG+1: $32
CO: $11.15
Hero: $69.15
SB: $3.65
BB: $12.10

Pre-flop: (6 players) Hero is Button with K[img]/images/graemlins/club.gif[/img] K[img]/images/graemlins/spade.gif[/img]
UTG folds, <font color="#cc0000">UTG+1 raises to $0.85</font>, CO folds, <font color="#cc0000">Hero raises to $2.9</font>, 2 folds, UTG+1 calls.

Flop: 5[img]/images/graemlins/heart.gif[/img] 8[img]/images/graemlins/club.gif[/img] A[img]/images/graemlins/heart.gif[/img] ($6.15, 2 players)
UTG+1 checks, <font color="#cc0000">Hero bets $6.15</font>, <font color="#cc0000">UTG+1 raises all-in $29.1</font>, Hero ?.