3/6 limit 8-handed. I have UTG+1.

UTG limps, I limp, MP limps, MP +1 limps, CO folds, button calls. SB(Villian) completes, BB checks. Loose table obviously, and in EP I like to check out a flop before pushing a medium pair.

Flop comes . Checked to me and I bet. MP folds, MP+1 calls, button folds, and Villain raises. I decide to call here because I have no doubt I have the best hand. MP+1 also calls, everyone else folds. Pot is 13 SB's.

Turn is . SB bets, I raise, MP+1 folds, SB calls.

River is . SB checks, I bet, SB raises, I reraise, SB 4-bets, HERO???

This is where I have my question...SB is not a rock, but isn't completely loose either. I'm sure he has a hand. Just curious on any opinions here on my river play...