I don't have a say in the baby's name other than middle name..

Samantha

I'm having a baby boy with my ex boyfriend (we live together so he doesn't seem like an ex tbh) and I'm only 4 months along, so I didn't know anything was set in stone. We had talked about having him be Andrew like his dad, because he's a jr, by really he isn't. He wants him to be a third but he wouldn't be one anyway because he wouldn't have the same middle name?? None of them have the same middle name so it doesn't make sense to me.. At first the baby's name was Andrew Isaac but the farther I got the more I hated the name and wanted to change it to Isaac Andrew and I tried to just bring it up and he told me no & that there's no other option it's a tradition but there's only 2, so it doesn't make sense and I don't like it. He said "it's MY son" & when I replied with it's not YOUR son he's MY son too. He said no, I don't understand and his family already did this and this but idc I'm only 4 months that's their fault for not waiting longer. He said something about him and his family already had it planned and I'm like wait what? I don't give a damn about what his family OR my family thinks. It's OUR baby not theirs. I'm the mother I should have a say especially if I do not like it!!! Help :(