Struggling to accept my child wont be my fiance's first

Hi guys. I just found out that I am 10 weeks pregnant!!! I'm absolutely beaming. There was some question as to my fertility so I'm ecstatic. But now that its happening I'm saddened. He has two children whom I accept and love. But his ex is terrible and controlling even today. She also refuses to meet me and doesn't agree with our relationship. It's hard for me knowing this is my first time and not his. I'm jealous of their experience. I'm jealous that they got to go through everything for the first time. I feel like that experience has been taken from me. I feel as though I'm being unfair though... my father and eldest brother passed away years ago so I'd like to give my last name to my son to carry on the family name. My fiance LOST it at this. Hes infuriated by it and "wont let it happen" I feel as though my fertility issues and his already having two children should mean I get to cherish this pregnancy and make the bigger decisions. Sorry I'm just venting I suppose. But I would love opinions please.

Thanks in advance 🤗

EDIT

I just wanted to mention that he previously agreed to me giving my children my last name. Apparently he just said that because he though it wouldn't happen since we were struggling for so long