I am sorry for your pain and confusion. Welcome to SI. You will find support and guidance here.
I sorry for your double betrayal by your H and BFF. There is a thread in I Can Relate dedicated to double betrayals. You can find specific support there.
There is a great book you and your WH should read "Not Just Friends".
There are a few post here in Just Found Out you should take a look at too:
Boundaries and Consequences 101
A Great Post for Newbies
Before You Say Reconcile
Your WH needs to establish NC with the OW. Your WH needs to stop discussing person information with others. The two of you need to decide on Friends Of the Marriage (FOM). These are people that you trust that have the best interest of you marriage at heart. You need to establish what your boundaries are and what the consequences are if they are broken.
Keep reading and posting here. You will make it through this.