very badly played KK hand

My image is very laggy (I'm raising almost every time I'm on the button, and I rarely limp)

PokerStars No-Limit Hold'em, $1.00 BB (6 handed) FTR converter on zerodivide.cx

UTG ($72.30)
MP ($95.20)
CO ($48.50)
Hero ($136.50)
SB ($28.50)
BB ($140.45)

Preflop: Hero is Button with K:spade:, K:club:.
UTG calls $1, 2 folds, Hero raises to $4, 1 fold, BB calls $3, UTG calls $3.

Flop: ($12.50) 4:spade:, 6:heart:, 2:heart: (3 players)
BB bets $10, UTG folds, Hero calls $10.

Turn: ($32.50) A:heart: (2 players)
BB checks, Hero checks.

River: ($32.50) J:diamond: (2 players)
BB bets $30, Hero folds.

Final Pot: $62.50

I'm pretty sure he had a set here, but I should have raised his flop bet to make sure.

take a stab at the flop to know where you really stand... the bet flop, check turn line seems like the heart draw for some strange reason. the flopped straight would be inclined to check/raise the flop or turn for full effect

this does look a lot like a set. I think you made a good laydown on the river. I think you should have raised the flop tho.

I don't think he leads out hard, as in this case, on the flop with a draw against the original raiser. Actually I think opposite of another in the thread that the flush scared him a little but since you didn't bet it, he figured you hadn't got it.

Set or straight, most likely set.

T.