First of all, you should respect your husband's privacy, which means he has the right to decide whether his mobile phone can be viewed. You'd better not look at his mobile phone without his permission. Even if you suspect that he did something wrong, you should communicate with him first, instead of checking his mobile phone directly.
Secondly, if you want to check his mobile phone, you must first establish enough trust and respect. If you can establish a relationship of mutual trust and respect, you can try to discuss it with him and check his mobile phone after obtaining his consent. If you don't get his consent, you'd better not check his mobile phone.
Finally, no matter whether you decide to check his mobile phone or not, you should respect his privacy and establish a relationship of mutual trust and respect with him. Through daily communication, you can better understand his personality and behavior, rather than judging whether he is loyal by looking at his mobile phone.