Glad you found SI site but so sorry to have you here. I am 9 months out from D-day and it does get better. Have had some times that we back peddle but that seems to be the thing. Around 6-7 month out was really bad and it could have been related to the cold snowy winters and long dark times.
Is your spouse totally transparent? Do you have access to cell phone, emails, computers and etc? Need to and I still check just to make sure when things maybe are too good or not. He has lost all privacy and cannot change pass words without telling me. I rarely check any more, but I did a lot early on to give myself peace of mind......and him some understanding that if he did not follow the MC's guidelines, he was telling me to leave.
The self doubt is there for a long while....and understand it can take a long while for it to get better. It is strange to me how another female can have no affect on me for years and the affair has changed so many things in our relationship and how we relate to others. Trust is gone....
Take care of yourself and know you can always share anything here.