Over reacting?

ronnie
So today i went thru my boyfriends phone and i saw him snapchatting this girl, and when i asked him about it he said she's an old friend she wanted to see what i was doing. In my head i was like wtf! Why?! But i didn't say anything but now i feel so pissed. Because if he found out i was talking to an old guy friend he would be just as mad if not angrier. He never hides his phone from me he doesn't keep us lowkey he's always putting me on his snapchat and facebook but it just sucked because when i was going thru his friends list i saw his ex on there and i was just speechless. I know he's not really mine he's his own person. I just wish i wasn't so jealous and didn't let those type of things bother me and i wish i would just be worried about my self and focused more on my happiness and making myself happy rather then making my self believe that he is my happiness. Any advice ladies? I really care about him and i still want this to work we've only been together for 5 months and i don't want my jealously to drive him away or make him distance himself from me so any suggestions on how i should act or anything? I wanna be mature about those types of situations and handle it like a women would.