At 44, you are very lucky to have a 26-month-old son. The fertility rates for women over 40 drop dramatically, so if you conceived your son at 41, you were extremely lucky. I am 44, I started doing fertility treatments with a reproductive endocrinologist at 42 and 10 months - I had regular periods, still ovulated, everything was normal, but I didn't understand that a woman age 42-43 has only about a 5 percent chance of getting pg and carrying to term, due to old eggs. The body uses up the good eggs first and what that means is by the time you hit 35 many of them are gone, by 40 most of them are gone. At 44-45 you have about a one percent chance of getting pg and carrying to term. That's because the eggs you have left are not good - they are chromosomally abnormal. In addition, your chances of having a child with Down's Syndrome is about 25 percent - extremely high. Those celebrities you see having children at 45 and older - they are using donor eggs. This is commonly known in the donor egg support groups. I ended up having to go to donor eggs and even with that I have had two miscarriages - turns out I had a thyroid issue that was not previously identified.
It sounds like you and your husband aren't on the same page. I think you really need to resolve this issue as soon as possible- here's why: If you want to have another child, you have a couple of options, donor egg, donor embryo or adoption. With donor egg or embryo, you will have to go through the fertility treatments - shots, etc. With adoption, I've been told that if you are 45 or older, the time it will take you to be matched will be longer, because with open adoption, which is the prevalent adoption method today, birth moms choose the parents and they often don't want parents 45 or older because that's how old their own moms are.
I don't tell you these things to be the bearer of bad news, but because there is so much women don't know because no one tells them or talks about it until it is too late. I see many women on my donor egg support group that are in their mid-to-late 30s who already have diminished egg quality or quantity. I wish someone had told me at 35 what my chances were for having a biological child after 40 - I probably would have acted sooner. That being said, if you want to have a sibling for your son, I would immediately go to a fertility clinic and talk to them about donor egg or start looking into adoption.