Villain is 8.6/6.3/0

Party Poker No-Limit Hold'em, $ BB (10 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

SB ($13.30)
BB ($31.12)
UTG ($3.91)
UTG+1 ($5.65)
Hero ($27.05)
MP1 ($38.83)
MP2 ($20.83)
MP3 ($18.62)
CO ($11.80)
Button ($17.02)

Preflop: Hero is UTG+2 with 2, 2. SB posts a blind of $0.10.
2 folds, Hero calls $0.25, MP1 calls $0.25, 5 folds, BB checks.

Flop: ($0.85) 7, 4, 2 (3 players)
BB checks, Hero checks, MP1 checks.

Turn: ($0.85) 3 (3 players)
BB bets $1.5, Hero raises to $5, MP1 folds, BB raises to $8.5, Hero calls $3.50.

River: ($17.85) A (2 players)
BB bets $22, Hero folds.

Final Pot: $39.85

Flop is 742 with a flush draw, Im second to act and check. Here I probably should have bet, but the player after me was fairly LAGG so I was planning to check raise. The turn comes and villain, out of the BB, bets almost twice the pot, I dont have any idea what he could have here, but he hasnt been aggressive. I raise hoping to simply take the pot down here, and then he min 3-bets me, I call looking to fill up or get a cheap showdown. There were 3 cards to a straight on the board so I thought he might have hit, but I still dont understand his overbet of the pot. Anyways, river comes an Ace giving 4 cards to a straight and he pushes, I fold. I think I have to fold that river, but what about my other streets, how should I have played those?