Boat gets CRAI on river

[AssFrister]

I didn't have any reads on villan at the time. I have been rather quiet on this table and so it has taken a bit of a back seat. If I had to give a read on this game in general for the typical opponent I'd say they are not very good, not thinking.

Effective stacks ~120BB
6 Handed

I raise A[img]/images/graemlins/diamond.gif[/img]J[img]/images/graemlins/diamond.gif[/img] UTG to 3.5BB and villan calls in the BB.

Flop: A 9 6 rainbow (Pot = 7.5BB)
Villan checks, I check.

Turn: A (Pot = 7.5 BB)
Villan checks, I bet 5BB, Villan calls.

River: 6 (Pot = 17.5 BB)
Villan checks, I bet 9BB, he CRAI for 111.5BB, I vow never to click "bet" again...

From your experience how often am I chopping and how often am I getting stacked here? And how often is it somthing stupid? Though I don't see how I can ever be winning this outright.