Insecure?

So I’ve been with my boyfriend for almost Two years this July. He is always on snap chat. About a year ago some girl Facebook message me that my boyfriend was snap chatting her. I didn’t answer her back. I confronted him and he said he was just sending snap chats of the dogs. I got a little angry with him and let it go. But, it still feeds at the back of my mind. A few months ago a girl snap chatted him and they went back and forth snap chatting. He said there’s nothing to worry about. I feel very worried. Because I’ve been in situations like this before and it has made me untrustworthy of men. He told me he only loves me and only me. Sometimes I don’t believe it. Like am I unattractive or does he have emotional issues. We’ve discussed how I feel about him snap chatting other girls he understands but sometimes I feel like he’s always doing that. I know he snap chats with a lot of his guy friends but this really bothers me. I have been very anxious about this and I just want to let it go. Any advice?