Husband with other girl

Hi, i and my husband was 28 yrs old. we r love married before 5 yrs. their parents accepted. but my parents accepted now only. A that time he doesnt have job. i was at work and did every thing for him and his family. bot for 4 yrs he is at work. now getting good salary. now i'm 9 months pregnant for second delivery and in my moms home. for last 1 yr my husband is having conact with another girl. that i came to know now 1y. but now that girl is going to get married. now i'm in parents home. after three months only i will go there. that time 1y her marriage also. he is telling me now for these months i will have contact with her. after that i will be with u only and i will talk with her nothing other than that. how can i believe him?