please help I need some advice girls!!

Ok so me and my boyfriend been together for 5 years almost 6. We recently got back together but he has a passcode on his phone that bothers me so much because I dk why he would want to keep the password from me. He's the type of guy that never ever goes thru my phone or anything. I just want him to have privacy to himself and I want to be able to trust him. Honestly I feel like the only reason why he's locking the phone is because he might be watching porn and he knows I don't I don't like that. I ask my friends for advise and they tell me it's no biggie that he needs to have his privacy I have a passcode on my phone as well and does not know about it he doesn't even ask me what's my passcode. So please help me? What do y'all think I should do? I really don't want to give on him because we've been together for a long time.