<human>: Can you provide a brief overview of the text?

I have been dating her since early January 2014. 

Everything has been great. We get along amazing. I'll be the first one to admit to instagram stalk her. I check the pictures she likes. I'll be 100% honest and you'll have to trust me on this one - I do it not because I distrust her, but mainly because I want to see what she finds interesting and for ideas for dates/gifts. And considering I follow few people on ig, the 'liked stream' of my the people I follow is a part of the fun, in a way. But I digress - she generally likes pictures of birds (she loves birds), her coworker's friends, and Peter's photos.

Peter is a guy with 700 followers and follows 900. They follow eachother since around December I believe, but I could be wrong. My girlfriend generally does not like any of her 'closer' guy friends' pictures. She's rather selective with her liking. Yet she has liked about 6 of his last 30 photos on instagram. She has never spoken to me about him, even if she usually tells me about people who she likes and are part of her life. Bottom line is that this behaviour is not typical for her from what I've seen.

I checked on facebook, it seems like they are not friends on Facebook and have no friends in common.

Coupled with the fact that admitted cheating on one of her ex (trickle truthed, I'd imagine she cheated on more than one of her exes), and on one other occasion being excited to see her ex at a party we went to, her fucky behaviour is making me anxious.

I think it's well established that I'm kind of crazy, no need to remind me of that. My question is whether I am justifiably anxious and put off by her liking so many of this guy's selfies. And also, how do I bring my discomfort, or should I bring it up at all?
<bot>: girlfriend likes an abnormal amount of this guy's selfies on instagram. I am not comfortable with that - am I right in being uncomfortable and how do I bring it up?