I had no idea he was bisexual

Found out my husband of 10 years has been having affairs with men. We have been together for 16 years and I had no idea he was bisexual.
He has been in a relationship with a man for 18 months plus messaging, sexting and meeting for sex with several other men that I know of.
I feel like the world is crashing down around me, I have known for 2 months but don't feel like it's getting any easier to get my head around.
I guess I don't know to walk away or to try to get through this.
Any advice?