Divorce ground

Sir, I married a girl in may 2014. After 1 month I could know that she had an affair with married person through exchange of messages among them. But with the assurance that she will not be involved in him anymore, I excused her. But later on she started to call him and speaking hours together and more frequently. Now I don't have any evidence of conversation but I have call records. She is (8 months) pregnant also. I want to have divorce from her. So I request u to tell me that is divorce possible and if yes how will b its course. And will I get an opportunity to have DNA test of borne Baby and how.