Hand 1: 99 in BB after a break

I haven't played poker for a month or so and I'm trying to ease into it again. So what is wrong with this hand (or hand 2 in another post)? No real reads yet except MP looked like the tightest one at the table, a lot tighter than me the few hands I had seen.

PokerStars 3/6 Hold'em (5 handed)

Preflop: Hero is BB with 9[img]/images/graemlins/diamond.gif[/img], 9[img]/images/graemlins/spade.gif[/img].
1 fold, MP raises, Button calls, SB calls, Hero calls.

Flop: (8 SB) 5[img]/images/graemlins/diamond.gif[/img], A[img]/images/graemlins/diamond.gif[/img], 3[img]/images/graemlins/diamond.gif[/img] (4 players)
SB checks, Hero checks, MP bets, Button folds, SB calls, Hero calls.

Turn: (5.50 BB) 3[img]/images/graemlins/spade.gif[/img] (3 players)
SB checks, Hero checks, MP checks.

River: (5.50 BB) 5[img]/images/graemlins/heart.gif[/img] (3 players)
SB checks, Hero checks, MP bets, SB folds, Hero raises, ...

Too small pot to try or does that make it better? Bad I idea when I'm an unknown myself? Feel free to rip any street apart if you need to. [img]/images/graemlins/smile.gif[/img]