He is Cheating On Me

Good morning. Pls  I need some advice. I am a lady aged 24,married 2 a man aged 33 en we hav a child 2gether. i feel like i cant  this anymore or else i might be tempted 2 do something evil .things hav not been well since last year November. I  suspected that he was cheating on me en my suspicions were proved ryt in december wen he started spending nyts out, i realy ignored all this end welcomed him in a nice way .now things have gone realy bad, wenever i cal him he neva picks my calls bt wen he cums home en this woman calls he picks up the call in my presence sayin yes baby, en after that, he leaves the house even at 23hrs.  He recently told me he has married the same lady en its up 2 me 2 decide if i stil want 2 b wit him. i love him alot but am not willing 2 be kupanga  (with a polygamy).wat do i do?he cums home twice a week. his people have tried talkn 2 him but 2 no avail.i dont knw wat 2 do coz as it is am pregnant again en he knows this...pls people help me,wat do i do??