Thanks for writing to Just Answer.
It doesn't sound like much has changed in the five years you were separated. Either he has something to hide (which would be my guess--taking the cell phone into the shower is excessive.) or you have been pushing him away with distrust.
And even if you have been distrustful, as the one who was unfaithful, he should be making his life an open book now, not hiding it from you.
It doesn't sound like you two have much of a relationship, if you are just roommates after just a year of being back together.
I think you should go to counseling alone, and figure out why you are willing to settle for living like this. Most women would not tolerate it, and would make him leave. It may be that his infidelity had a profound effect on your self-esteem since it involved the two people closest to you. Working on feeling better about yourself will make you care less about checking up on him and his cell phone, and more about building a better life for yourself, with someone who cares about you and wants you to be happy and secure.
Here's a link to help you find a therapist in your area.
I wish you all the best!