It’s unlikely that you have made a terrible mistake. Otherwise you , your husband, your referees and your social worker would probably have spotted it by now.
So it’s much more likely that you are not thinking rationally because you are grieving and / or depressed.
Adoption is not the same as having a birth child, particularly at the stage you are at. Because you’ve not had the months of preparation, emotionally and physically . And you don’t have the oxytocin from BF.
However once you get through the initial stages, parenting an adopted adopting a child is very very similar to parenting a biological child. I say this as someone who has both, I forget which ones are which.
And many other adoptive mums will say the same.
However what adoption won’t fix is your grief for not being able to conceive, keep pregnant, give birth, breast feed, and have a child who is biologically yours.
Many find that their grief about these things is changed by adoption, but for some people it never goes away completely .
But the only way to cope with this grief is to keep going through it. It won’t go away if you give the baby back.
What baby needs from you is her physical needs met and lots of talking to and cuddles . And preferably as much physical contact with you as possible.
Can you do that ? You don’t need to love her , I’m fact it would be quite unusual if you did.
She cant see that you are cold and numb. She will not suffer as long as you do the above. I’m not minimising your suffering but don’t make it worst by thinking that you are harming her, you are not.
Please go back to your doctor today and tell her how you are feeling. See if she thinks that meds would help.