Nut flush river decision

[MoreWineII]

I haven't posted a hand in a loooong time mostly because I haven't played in a looooong time, so keep that in mind when you read this.

I played this hand in a recent very loose-passive 3/6 b&m game:

I get a5 [img]/images/graemlins/diamond.gif[/img] on the button. Four players limp, I limp, SB folds, BB checks.

Flop: qj3 [img]/images/graemlins/diamond.gif[/img]

Checked to me, I bet. Youngish ABC-ish player calls. This was the most aggressive guy at the table other than me, which wasn't saying much. He wasn't really imaginitive in any way, mostly the impression I got was that he liked to pump his draws.

Turn: j [img]/images/graemlins/club.gif[/img] He bets, I raise, he calls.

River: 3 [img]/images/graemlins/spade.gif[/img] He bets, I fold. I think it was 9 big bets to me at this point.

How close was my river decision? Did I fail spectacularly? My main reasoning was this: I don't think this hand gets folded by many players this guy usually plays against. I'd been at the table about an hour and I didn't believe he had any great read on me as anything different. Therefore, I think he expects me to call. Which led me to believe that he wasn't bluffing. I felt like it was a pretty close decision and this line of logic led me to fold.

This decision is still kind of bugging me a few days later so I thought I'd ask.