Bern, What are your plans with all this info. Why spend the money on a PI? You already know she's lying. Does it really matter why she's lying? You are letting her cake eat. I would be confronting her now about her lies. Cuddling at night time, telling her about her day and holding your hand, why are you putting yourself through this?
Confronting will do nothing. You have to take action to reaffirm your boundaries on your spouse seeing other people. Simply confronting says "I know you're doing this and I'm not doing anything about it".
H 34 W 29 BD 3/12/18 Divorce Busted Spring 19
It is not things that bother us, but the stories we tell ourselves about things.