Too Aggressive?

I've tried (the last week or so) to play more aggressively, raise PF, bet when there is a decent made pair (such as the hand below). Maybe I played this one too aggressive:

Paradise Poker $0.10/$0.20 Hold'em (9 handed) FTR converter on zerodivide.cx

Preflop: Hero is MP3 with 7[img]/images/graemlins/club.gif[/img], J[img]/images/graemlins/club.gif[/img].
UTG calls, UTG+1 calls, [color=#666666]1 fold</font>, MP2 calls, Hero calls, CO calls, [color=#666666]1 fold</font>, SB completes, BB checks.

Flop: (7 SB) 6[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/diamond.gif[/img], J[img]/images/graemlins/heart.gif[/img] [color=#0000FF](7 players)</font>
SB checks, BB checks, UTG checks, UTG+1 checks, MP2 checks, [color=#CC3333]Hero bets</font>, CO folds, SB folds, BB calls, UTG calls, UTG+1 folds, MP2 calls.
<font color="blue">Checked to me, why not bet??</font>

Turn: (5.50 BB) 4[img]/images/graemlins/diamond.gif[/img] [color=#0000FF](4 players)</font>
BB checks, UTG checks, MP2 checks, [color=#CC3333]Hero bets</font>, BB calls, UTG calls, MP2 calls.
<font color="blue">Again, no one showed any stregnth, so bet again</font>

River: (9.50 BB) K[img]/images/graemlins/spade.gif[/img] [color=#0000FF](4 players)</font>
BB checks, UTG checks, MP2 checks, Hero checks.
<font color="blue">Not sure why I checked through on the river, but I did. &lt;shrug&gt;</font>

Final Pot: 9.50 BB

At the showdown, I was outkicked. Was I too aggressive here?

Another question I have is I play tight most of the time, folding about 70%, and when I enter PF for a raise, I usually end up 2 or 3 handed. Am I playing too tight, and when I show stregnth (AA/KK/QQ/AK/ etc...) people notice that right away and fold out. Would it be better to limp in these situations, then maybe raise the flop when/if I hit to build the pot?