Relationship advice.

I have no access to his phone whatsoever, but I feel like he’s talking to someone mainly on Snapchat etc. I don’t even know his password or anything. I just wonder what I could do to make me feel at ease. I know probably nothing but hey. I’m sure someone has felt like this before and maybe it’s nothing but it’s the constant when I walk up while he’s on his phone he puts it away quick after texting. There’s no way I’ll ever know.