My husband and I had been living apart for 3 years. Despite this we slept together and I fell pregnant. My son is 2 months old. He knows he is his, but I didn't put his name on the certificate- I left it blank (he never wanted the baby). We are now reconsiled and I want him on it- and want to amend our sons double barelled name( which is mine) to just his fathers bit of the name( to be the same as our other son). Is this possible? How do I go about it?

Contact your local county clerk or whoever issues birth certificates. They can explain the procedure as it will differe from locality to locality.