he won't admit he has a current girlfriend

Desperately need advice

I met my narc boyfriend 2 1/2 years ago. He did the whole love bombing thing like a pro. I did not know anything about narcissism before I met him so I feel for it hook, line and sinker. My friends did too. They couldn't believe how sweet and loving he was to me. We live a good distance apart and he also would travel here and there for work. The first year was amazing. Then I learned he cheated on me with someone. Not just a one night thing, he had a relationship with her for like a month! I never had a clue. I found out because he had posted on his facebook that he got married.