Letting him bluff or am I an idiot? 25/50 UB hand

[bogey]

So I have a few beers in me and decide to sit down at the 25/50 for the first time. Opponent in this hand seems like the typical kind of loose/aggro pretty good 25/50 player, although this is just my 2nd orbit at the table. He probably has no read on me, except maybe I'm kind of tight, but hasn't seen enough hands to really tell. I have slightly less than 5k and opponent has me covered.

It's 8 handed now.
Villain limps UTG+1. Folded to me in the BB with A [img]/images/graemlins/spade.gif[/img]K [img]/images/graemlins/heart.gif[/img]. I check.

Flop ($125) 8 [img]/images/graemlins/diamond.gif[/img]9 [img]/images/graemlins/diamond.gif[/img]Q [img]/images/graemlins/club.gif[/img].
I bet $125. Villain calls.

Turn ($375) K [img]/images/graemlins/spade.gif[/img].
I check. Villain bets $375. I call.

River ($1125) 2 [img]/images/graemlins/heart.gif[/img].
I check. Villain bets $1125. I call.

Flame away.