Just sat down... Villian has about half a stack

Full Tilt Poker
No Limit Holdem Ring game
Blinds: $0.25/$0.50
4 players


Pre-flop: (4 players) Hero is Button with
UTG folds, Hero raises to $1.5, SB calls, BB folds.

Flop: ($3.5, 2 players)
SB checks, Hero bets $3, SB calls.

He very quickly called the flop bet. I don't see him doing that with a pair of 3's, so I'm guessing he either has a King or a flush draw.

Turn: ($9.5, 2 players)
SB bets $3.5, Hero calls.

It's odd that he's leading into me like that (and good for him if he's ahead, as I would have checked behind). I don't think I want to re-pop it with the flush and pair of Kings out there, but he's certainly pricing me in to draw for another diamond.

River: ($16.5, 2 players)
SB bets $5.5, Hero ????

Missed the flush, but again it's a small bet. Am I good here enough times to warrant a call?