Is divorce a good idea?

My situation is complicated and hard to understand. Its a long story but id appreciate some good wisdom and guidance. Im only 21 and i have a child with my husband. He walked out when i was pregnant and said he couldnt be a father, through that time he was dating someone else and was engaged to her but when i met him i knew he was divorced. This is his second marriage. We got married to try and form a family (since he was adopted and never had a good childhood or his biological mom and dad) well soon after our marriage i began to find out things about him that i disagree with and would never put up with in any relationship. I find out he was never divorced when we were together, it was finalized last june. And i also found out he still emails his ex wife and an ex gf from high school. I found a video where hes with another woman (sexually). Ive been harrased on fb by another woman who claims to have had several sexual encounters with him. On top of all this he is deployed and i found out that while he was in hawaii, he called his ex wife and ex gf. Why do i stay? Becasue i believe people can change and god can do the impossible. I dont believe in living in the past i believe in forgiveness, but as much as i do i will not be someones option and be considered a wife only on paper. I asked for the divorce. My family doesnt like him, his mom tells me to give him a chance. But my heart is torn in two different directions. I dont know what to do, i dont want to quit and get a divorce...