Im giving you my take on this before reading other's replies so as not to bias my response.
Its only 20 hands so your saying you dont have any real reads on villain so if I were you I would likely interpret his actions at face value for the moment.
First pre, AQo isnt the greatest hand to call a raise with OOP especially with an unknown villain. If you know him/stat him as loose..ok fine maybe even 3bet him but in a bubble like that where your at, I would just fold. I understand wer 4 handed so I also understand and respect your raise, so im marginally ok with your decision.
Flop: Good bet on the flop, I might have bet more towards 4$ but its cool.
His re-raising on somewhat of a relatively dry board after youv shown a lot of strenght preflop, and followed up with the flop bet tells
me this guy is either a bit of an agro player reraising you with a diamond draw or, more likely has a pair at or near the top of his range i.e QQ+, AK.
I mean without further info what could he be raising you with after youv shown him a lot of strengh pre and post??
Without additional info hard to tell if hed do what he did with pkt22 or 44 pre.
In my opinion your either barely ahead or way behind here.
edit: I realise im advocating folding TPTK here 4-handed so take this with a grain of salt but IMO at these stakes, bets and raises usually mean business. I also agree with the previous posters comments as well.