Flop agression was due to drawing for the nuts flush draw. After "hitting it" with the turn card and getting 3-bet, I was kinda lost to as where I was with my hand.
Hand converted with online PokerStrategy.com hand converter:
$0.05/$0.1 Fixed-Limit Hold'em (8 handed)
Preflop: Hero is BB with A:c, 7:c.
UTG2 raises, MP1 folds, MP2 calls, MP3 calls, 2 folds, SB calls, Hero calls.
Flop: (10 SB) 7:h, 3:c, 6:c (5 players)
SB checks, Hero bets, UTG2 calls, MP2 calls, MP3 calls, SB raises, Hero 3-Bets, UTG2 folds, MP2 folds, MP3 calls, SB caps, Hero calls, MP3 calls.
Turn: (12 BB) A:d (3 players)
SB bets, Hero raises, MP3 folds, SB 3-Bets, Hero calls.
River: (18 BB) 8:h (2 players)
SB bets, Hero calls.
Final Pot: 20 BB.
Results follow:
Hero shows two pairs, aces and sevens(Ac 7c).
SB shows three of a kind, sixes(6h 6d).
SB wins with three of a kind, sixes(6h 6d).
I like your donkbet but it would be horrible if it gets checked through what might happen when UTG2 decides to not bet his overcards which i wouldnt do as well being in his shoes. So you took the initiative. Fine! You were lost but somehow you took the right decision, even though intuitively.