How to check on spouse phone

Is there anyway to check spouse wadaapp or/and messages despite it was password locked and not him knowing? Need IT experts in this. IPhone Reason of doing: I suspect he is cheating on me. This is not the first time, he had verbal cheating by talking to girl when I am pregnant with number 2. He said why he was doing this was because i never had much sex with him and we even at the verge of divorcing. I find him too self centered, I was so tired with taking care of number 1 kid and pregnant and he has such expections of having numerous sessions. I decided to forgive him for the sake of my 2 children. After I gave birth, I tot things are better and we have slightly more sessions when he request. But he is expecting more! I am not his sex slave. I suspect he is cheating on me again after I rejected him last week due to tiredness.