I dont know when I am ahead

[sds4255]

I play tight aggressive poker at the 2/4 limit online. The problem is I dont think I am extracting the maximum amount of value out of my hands bc I am always affraid I am up against the nuts.There are tons of examples I could give this one being the most recent and probably not the best bc of my call after the flop( I ll take comments on that too) Here is an example:
Dealt to Hero [Qc Ac]
early 1: calls $2
Hero: raises $2 to $4

Mid 3: calls $4Late 1: calls $4

early 1: calls $2
*** FLOP *** [5c 9d Th]
early 1: checks
hero: checks
mid 3: bets $2
late 1: calls $2
early 1: calls $2
her0: calls $2
*** TURN *** [5c 9d Th] [As]
early 1: bets $4
hero: calls $4
mid 3: folds
late1: calls $4
*** RIVER *** [5c 9d Th As] [7d]
ealry 1: bets $4
hero: calls $4
late 1: calls $4
*** SHOW DOWN ***
early 1: shows [Ad 6d] (a pair of Aces)
hero shows [Qc Ac] (a pair of Aces - Queen kicker)
late1: mucks hand
hero collected $49 from pot