Needing advice..

So yesterday after i came out from the restroom back into the living room my boyfriend asked me to put his phone on the charger amd then try to get into his phone and i couldnt and he had the biggest smile on his face when he put a fingerprint password on his phone and i couldnt get in it and mind you the whole 8 months we have been together he has never had a password on his phone..when i asked him why he made an excuse about having it because of his bank account.. like really im not stupid... so i feel like he has something to hide like hes cheating on me but idk.. what do yall think?