You form very deep attachments which is good.
But you also hurt deep and find it hard to forgive any disappointment.
One sure thing I know is that bottling such hurt takes its toll on people, the carefree easy look is gradually replaced with a sad look and it changes someone to a bitter introvert.
You can try not getting to attached for a starting so you don't get hurt when disappointed.
There is a lady I introduced to NL that had similar case even though it wasn't her best friend that was caught with her husband. She writes her story here now with lots of followers, she has finally let gone of the hurt and dated some few people. She grew big from depression and had health issue but since she has looked ahead and tried to make the best out of life she is doing great.
Just know that men are programmed to be sort of polygamous but not all double date.
I can send you the lady I spoke about's handle on request so you can draw inspiration from her.