100nl i get 4 bet by a reg

[shat4brains]

villian is ryancmu.
I dont like how i played this hand, should i have 3 bet this vs him in the 1st place or should i have flatted. I thought that he was very capable of raising light here against the limpers, and the times i have previously three bet him which is probably a lot i cant think of a single time he didnt 4 bet me so i honestly was considering shoving here because of this.

PokerStars No-Limit Hold'em, $1.00 BB (9 handed) Poker Stars Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

Hero ($108.95)
BB ($98.85)
UTG ($100)
UTG+1 ($54.70)
MP1 ($99.45)
MP2 ($148.80)
MP3 ($200.05)
CO ($100)
Button ($104)

Preflop: Hero is SB with A[img]/images/graemlins/spade.gif[/img], Q[img]/images/graemlins/diamond.gif[/img]. CO posts a blind of $1.
UTG calls $1, <font color="#666666">4 folds</font>, CO (poster) checks, <font color="#CC3333">Button raises to $5</font>, <font color="#CC3333">Hero raises to $18.5</font>, <font color="#666666">1 fold</font>, UTG folds, CO folds, <font color="#CC3333">Button raises to $49</font>, Hero???

thoughts?