I think hes cheating on me

I saw on my husbands phone that his most frequent use app is, facebook. Now, we both havent used fbook since the day we married, cause he doesnt want us to. He thinks its like a dating site. I went to log in to my acct, to see if his acct is active, but it isnt. So, i just know it that hes using a fake acct. All i can do now is, snoop. Cause talking to him didnt work. I know it isnt right, but i need to do it to know the truth. I rather get hurt by the truth, then get hidden from it. I need to know before i get pregnant again, because were trying for another baby. But, its odd that i had to see his fbook usage right when we were trying for another one. Maybe it was meant for me to see it, who knows. Anyways, his phone is a s9, its fingerprinted locked. And hes a very light sleeper, yall have any tips for me to crash into his phone, without getting caught?