Help!!!

So me and my husband just got back together we separated two weeks but are now back together I really want to work on my marriage and don’t want to go thru a divorce but... here’s the problem when I came back home he has a passcode too his phone. I haven’t told him anything yet since we just got back together I really don’t want to ruin things. I’m just tired of fighting and arguing with him because I truly do love him. I just don’t know why he changed his passcode! It makes me mad about it. But I really don’t want to ruin my marriage because of this. We are on the same phone plan I just care if he is not talking to no other girls or nothing like that. I know that If I wanted to check his calls I can but I really don’t want too. What should I do? Should I just leave it alone? What would you do?