How do you stop bring up past infidelity?

I found out my husband cheated a yr to yr and half ago. i found a hidden phone with nude pics of the girl still on there fr 2014. i found this secret phone 2 werks ago. There was also massive porn on it. i feel like i can't trust him. i downloaded a program to retrieve any deleted texts and emails and i got everything fr all the way fr 2014. there were no other messages besides what he confessed 1.5 yr ago so nothing new. we been n couseling 4 months for his porn issue but he obviously been lyin to me and the counselor the entire time with a str8 face. i find this so manipulative. i feel like how do i kno he wont get sneakier over time. we are ttc and he tells me the last time was when he told me 1.5 yrs ago.  i made him pay to take a lie detector test and be passed that he hasnt cheated since or watch porn in the past two weeks. How do i trust him again? especially, after being manipulative and wasting our money in counseling