Adding groups of chicks on Facebook..? Sketchy?

Caroline • Hey! Not much to say. Lol
So I was on my boyfriends Facebook wall, I was going to post a picture to share, when I noticed (for the 2nd time in less than a month) he had 3 new friends. So I clicked to check them out... All of them girls. The first time this happened it was about 6 or 7 he had newly become fb friends with and they're all girls!.. Idk what to think of this. He grew up in the town we live in and went to school here. So maybe they're high school friends? Either way it made me feel nervous.. We've been together for 3 years. And I've NEVER even had a wild hair of a thought that he would cheat on me. But I do believe that even contact online is mentally cheating. Relationships are more than just physical. They're very mental. Idk what to do to handle my suspicion.