Ancaire, the sadness and hopeless in very common. I had many days during the first few months after BD where I felt the deepest and most painful levels of sadness, loneliness, and hopelessness that I have ever experienced in my life. I can promise you it does get better, especially the more GAL that you do. You can and will have a fulfilling life without your H. I still find my grief comes in waves, but they are spread much further out.
I am sorry you had to experience such a horrible event, but I know how mind altering the gaslighting can be. I found myself doing things do out of character and I thought I was losing it many times when my H was lying and manipulating about his A.
Sending a big hug your way. Hang in there.
Me: 42 H: 40 M: 12 H moved out - 8/2015 I filed - 8/2015