secret marriage

So i was married then divorced we got back together but not married. During the last breakup when he said he needed a “break” he was cheating on me. But i found out he secretly married this woman and they have no kids together. Weve been together 20 yrs with 2 kids. He moved out got a place with her. anyway after bout a year he moved back in said he wanted to try. so its been almost 4 yrs and yet no divorce even though he keeps telling me he is going to do it. I feel he didn’t value our relationship enough to het this divorce right away. I believe even after he moved back in he was still seeing her and had some sort of sexual relations-with her. Ive caught him in lies several times. I dont know what to do. She even post pics of them togther on fb and he doesn’t even like when we take pics together because he doesn’t want to be on fb. Recent pic they went to lunch he said it was an old pic but she was holding a mask so it was recent last year . He said they just needed to talk about the divorce. Another time he went to a club with his friend and took her with him instead of me. He said she was just there, but they too pics and video of them dancing that she posted. Im at the point im constantly checking her fb page to see what else she has posted. Its driving me nuts and i just dont know what to do.