He had been folding to my raises before, but recently he had started calling when I started raising too much He's 12/4/1 after 50 hands.

Basically on the river I was trying to rep a really big pair (or quads?). Does the $15 do this or is it too small? I couldn't decide how much to bet. Or maybe the entire hand was played terribly, I don't know. Comments appreciated, thanks.

PokerStars No-Limit Hold'em, $1.00 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

CO ($96.45)
Button ($121.05)
Hero ($130.80)
BB ($124.70)
UTG ($59.50)
MP ($76.15)

Preflop: Hero is SB with 6, 6.
4 folds, Hero raises to $4, BB calls $3.

Flop: ($8) 7, 7, 7 (2 players)
Hero bets $6, BB calls $6.

Turn: ($20) 5 (2 players)
Hero checks, BB bets $14, Hero calls $14.

River: ($48) J (2 players)
Hero bets $15