BF with lavoo

hello its my first time here... I Met my bf on a website and since the first date we fell in love for each other. he is super kind, intelligent, lovable, cute... But yesterday I found a phone (another one) on his desk I grab it and making fun I tried to "spy (he was next to me) I tried to go in WhatsApp but then I saw the lavoo app. I clicked and the last conversation was on 09.03.17 and we met on 29.06.17 so he didn't cheat on me. But then I got furious and he almost cried saying he should have delete the app and that that phone was just an plan b phone because his was not working (and that is true). what should I do? pls don't say to break up for one misunderstanding I'm not giving up yet. UPDATED he eliminated the App and bought me a bouquet saying he was sorry and it won't happen again. He said that he didn't cheat because he texted them when he was still being single but he understands me. Today was our 5 months aniversary and it was beautiful.