Asking to see his phone is a bad thing?

So i asked my boyfriend so i can see his phone.. since he has a lock code i dont know it. He said no for what? its my phone my privacy i dont need to see it.. which i knew his passcode a year ago and found nothing but girls hes been snapchatting tryna meet up with them to smoke and do idk what when i was pregnant with my son and daughter lol… so yeahh i dont trust him and for him to change his passcode and tell me i shouldnt see it is stupid. Yeah it’s his privacy but I caught him already so now he changed it and says too not worry but what if he’s doing the same thing again? Lol 😂 i dont wanna get played or cheated on and embarrassed myself

He said he never met them he just messaged them cuz he was bored and social media isnt real lol but yet it hurts me when i seen that he was messaging girls .. but he said it isnt a big deal because he never met up with them while we were together just messaged them on snapchat. Lol am i being dramatic then or ?