Boyfriend and Kik

So I woke up this morning to my boyfriend hiding his phone from me. When I confronted him about it he admitted that he was talking to 2 girls on the app called Kik. We've been together 10 months and from my knowledge we have a really strong relationship. He claimed the girls were from years ago and are just friends. Am I crazy to think there's more to it than just this? Please give me some advice on what I should do about this situation.