Question on play

[kf4915]

I am a new user.

I recently was in a no-limit cash game 300 or so buy in 2-5 blinds 8 on the table. My first time playing against several of the players.

I am at position 4 with A [img]/images/graemlins/heart.gif[/img]K [img]/images/graemlins/diamond.gif[/img] offsuit.
3 folds to me, I bet $25.
5 folds, 6 calls, everyone else folds.
Flop. 5 [img]/images/graemlins/club.gif[/img]2 [img]/images/graemlins/heart.gif[/img]8 [img]/images/graemlins/diamond.gif[/img]
I bet $40, 6 calls
Turn j [img]/images/graemlins/club.gif[/img]
I bet $55, 6 calls
River 6 [img]/images/graemlins/club.gif[/img] I check, he goes all in with his last $40
I call
he had q [img]/images/graemlins/club.gif[/img]9 [img]/images/graemlins/club.gif[/img]

Now this isn't your typical bad beat story. The guy gives me some free poker advice and tells me "Dude, you played that had so badly". I ask "how so". "Dude, this is a no-limit cash game, you should have bet so much more if you wanted me out." I said "ok, thanks".

1. Is this true?
2. Should I be happy to play this guy?
3. I had a losing session that night, so I am second guessing many moves.