Advice ?

So me and my baby daddy have been on and off for about a year and in four months pregnant and we decided to get back together and try and make everything work and now the best friend that we share wants to be with me and I don't know what to do I don't want to be the reason they aren't friends anymore, but I don't want to lose him as a friend either but at the same time I don't want to lose the father of my child that I love more than anything can someone help and give me advice on what to do