Boyfriend liking other girls bikini pics

I know it’s stupid and I’m not usually like this but my boyfriend has been liking this same girls bikini pics. I don’t mind that he likes other girls pics, and I don’t usually look to see what he’s liked on Instagram but I came across it and noticed and I’m bothered by it.

Here’s a back story: my boyfriend asked me about this particular girl a few months ago and asked if I was friends with her and I said no. we just have class together but I don’t talk to her. Then I asked if they were friends and he gave a weird answer but came across as he strongly disliked her and started naming her negative traits

Liking pics is one thing but not ones when they are basically naked.... you guys probably think I’m crazy. It doesn’t help we are still on break from college so as of now we are long distance and I’m a tad paranoid. I just needed a platform to vent.