passcode on fiance's phone

hey everyone! I need some advice/opinions. so I've been with my fiance for over a year. he has always had s passcode on his phone since I met him. I was ok with it at first, even though I've never had a lock on mine. well found out he was hiding a drug addiction from me. at the beginning of June, he decided to get help and went to an inpatient rehab facility about a hour and a half away from home. while he was there, he made many promises to me, one being that he will no longer have a code on his phone and hide things from me. he finally gets released and things were great until about 2/3 weeks ago. all of a sudden there's a code on his phone. we are constantly fighting over this. he feels like I should just trust him and I'm trying to be a dictator... I tried to explain to him that if he had no code on his phone, I wouldn't want to go through it, but since he does, I feel like hes hiding things from me again. am I in the wrong?