Villian was 65/10/?? over about 30 hands.

I check-called almost every street. Bad play on my part?

After flop I put him on 2 pair or less or maybe flush draw. After turn I still had him at 2 pair maybe Ks and Qs and flush draw. After river I was thinking AT or flush? Then I though of ATd. But then why would he just bet half pot if he had the flush or straight? To keep me in?

PokerStars No-Limit Hold'em, $0.05 BB (4 handed) - Poker-Stars Converter Tool from FlopTurnRiver.com

BB ($13.59)
UTG ($6.34)
Button ($13.87)
Hero (SB) ($5.14)

Preflop: Hero is SB with 6, 6
UTG calls $0.05, 1 fold, Hero raises to $0.20, 1 fold, UTG calls $0.15

Flop: ($0.45) K, 2, 6 (2 players)
Hero checks, UTG bets $0.30, Hero raises to $0.60, UTG calls $0.30

Turn: ($1.65) Q (2 players)
Hero checks, UTG bets $0.70, Hero calls $0.70

River: ($3.05) J (2 players)
Hero checks, UTG bets $1.50, Hero ???