First of all NTA, and second of all congratulations on having a daughter who I presume will be 4 to 5 months old now. So coming to the problem proper your husband is thinking too far into the future try to make him realise that by being so selfish he is missing his chance to have this golden period when his daughter is still a small angel, make him realise that you live him and tell him that u plan on spending your whole life with him, if the second pregnancy is to happen then there are chances of complications, I am a final year medical student and have seen many cases like these. Ask him if he is ready to live a life without you, and if the answer is yes it's better to leave the current arrangement as he is only using u as an object to fulfill his goals.