I feel like there is a lot going on here (admittedly, some of which appears as red flags for me).

You have only been dating him for four months. That seems quite soon to be discussing marriage and children to me. The polygamy thing may not provide you with concern but does the practice of arranged marriage? Many Muslims practice this. The fact that you are of a different religion, ethnicity and cultural background makes a serious relationship quite unlikely. Have you talked to him about this specifically?

If he truly is talking to “multiple women”, it could be because his parents are setting him up with a potential spouse. I’m just putting this out there because it happened to me with an Indian, not Muslim, boyfriend. There’s a lot of pieces to your story that are written about after the initial post that are giving me pause. Guard your heart.