Obsession?!

I started the divorce process with my husband a week ago, when confessed he is in love with his ex girlfriend from 8 years ago. If that was not enough I wanted to know all the truth about them. I found a letter and e-mails he sent to her... In one of the e-mails he said he was stuck with me for the last 8 years and that she just needed to be patient until our divorce papers are done...
She was with him while she was married and she has a lot of issues also. She is older than him, have two kids and one grandkid. My husband does not like kids... and my understanding that was one of the things set him back few years ago... her kids are over 18 now and away from home. In the e-mail he sent to her, he said "I don't know how you are feeling about him , that is for you to decide so I will focus on us..." that means she is with someone else... however they are seeing each other and play the game on we should not be together because now he is still married... however, they are spending time together and seem she will not cut her relationship with the other guy until our divorce is final...

This information open my eyes, everything is too new and Ihave not contact with him for 4 days... however, the only thing on my mind is imagining together in what is used to be our home... having sex in what is used to be our bed, and spending time with my pets, which I had to leave because if I keep them he wanted to visit...

I feel I need to know more that will keep crushing my heart... knowing that this man did a lot of bad things to me and after 8 years he just changed me as nothing... I know I am wrong... but in some ways that is the pain that does not let me sleep... knowing he is happy... that both of them are happy playing this game, swearing how much they have loved each other during these 8 years he has been with me... while I am here crying and trying to pick up my pieces...

I pray to stop feeling this, but I think I am obssessed to try to know about them, because I think the more I know the more I open my eyes to this reality... Am I going crazy???