Looking through SOs phone

Amber • 17 years old. I've been with my fiancé for 2 years and 7 months😊

Is it wrong to ask to look through your SOs phone? I have severe anxiety and so, I get anxious over every little thing and lately his phone and the way he acts has been bothering me. He seems sketchy when I goes to his photos to look for a picture to show me and when he goes to message someone on messenger but has to go through his contacts to find them. And the other day he opened Snapchat and I saw his friend's name set as "my marebear" everyone calls her marebear. But she's not his. I talked to him about it and he said that she set it and he didn't pay attention. He says that he doesn't give a fuck what people change their name to in his phone, it doesn't mean it's true. And then a few weeks ago I asked ask if I could look through his phone because he said a few months ago that if I wanted to, then we could talk about it and I already made the mistake of going through his phone without permission a little whole ago. But I brought it up again when we were together yesterday and he asked me why and I explained and he said "you're the only one I want. You're the only one I love. If you weren't i wouldn't be wearing this Ring right now and I wouldn't be here right now" and it kinda reassured me, but my anxiety is still there and I don't know what to do about it😣