<human>: Condense the text into a few key points

I love my boyfriend very much.  We have open and honest communication.  We have a lot of fun together, and we also have a great sex life - once a day, at least.

So I know my boyfriend is a frequent masturbater.  This is fine, and doesn't bother me, as it doesn't get in the way of our sex life.

Buttttt....

We have been thinking about getting a dog.  Recently he mentioned that he commented on a friends photo of a dog she's giving away.  We have each other's fb passwords, so I logged on to see the photo.  When I went to activity log to find the comment, I saw fairly frequent searches for his ex gf.  Bleh.  Then, the other night he went to "poop" (aka masturbate) and he searched for her, and remained on fb throughout the time he was in the bathroom.  This happened again about a week later. So, yeah, he's masturbating to her.  Ughhh.

He was with his ex girlfriend for like 3 years, and they broke up about 2 years ago.  They hooked up in like January of 2014, but that was the last time.  We met over the summer.

A couple of months ago she called him and left him a long voicemail about how she wanted to talk, missed him etc.  He told me immediately, and texted her that he was in a new relationship with someone he cares deeply about, and that there was nothing to gain from talking.   She texted back trying to convince him to talk to her, but he refused, and ended the convo. As far as I know, that's the last communication they've had.

I just feel weird about the fact that he's masturbating to her.  But at the same time, I also feel like it could be completely harmless as I understand the fantasy vs reality thing.  I don't want to say anything about it if it's completely harmless. I'm just confused and I think I need some male perspective on this.
<bot>: Should I be concerned about my boyfriend masturbating fairly often to pictures of his ex girlfriend on Facebook? Do I say something?