Is my boyfriends phone behaviour a cause for concern?

My boyfriend (21) uses Snapchat and has a lot of streaks on it with some people who are his friends and others he met online before we met. A couple weeks ago I noticed a girls name come up with a snap and I ask who she was. He said it was just a girl he sends streaks to of random stuff and there's no real conversation happening. They have a 6 month streak like the rest of his friends do with him. When i asked to see what she sent him he refused to open it so I kept asking why won't he show me if its just a random pic but he was going out his way not to show me when I tried to take his phone by trying to snatch it back for ages. Its only when I left the room he opened it quickly, so when I returned the snap disappeared. I asked him why he did that, later he told me the girl sometimes sends selfies and he didn't want me to think something was happening when it's not. I looked through her chat with him and it was mostly them talking in a rude bantery way to each other a couple months ago. Today I noticed he wasn't opening the snapchat app or responding to snaps unless I couldn't see it or to respond messages from his guy friend (by clicking the notification) and then closing the app right away. He panics when I have hold phone and he can't see what I'm doing but I think I would too (I'm not hiding anything). Do you think I should be worried about this? He seems like a nice guy that wouldn't cheat, but his behaviour seems odd to me. I am his first girlfriend so I don't know why he would. Is this just a privacy thing? should I check his phone?
1 mo
By the way the girl lives in an other country and they have not met before.
Is my boyfriends phone behaviour a cause for concern?
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