Hello OP do you mind me asking, where is your family in all this, do you have rl support? After your baby is born I bet you will decide that he or she is too special to be around people who begrudge their existence.
His DM may well have kept quiet or she may have discussed with him but was asked not to 'rock the boat' by making it public.
He may have hoped you would just melt away so yes he may be embarrassed you approached his DM. Compared to being dumped after the news you were expecting, carrying a baby for nine months and going through birth I think a grown man can handle that. He may have big plans with his gf who could very likely be totally in the dark about this. That's not your problem! As to whether he denies the child is his, well that will soon be sorted following your baby's birth. He must realise a DNA test will establish whether you are being truthful.
Because you weren't married when you conceived, quoting from
www.gov.uk/register-birth/who-can-register-a-birth
The details of both parents can be included on the birth certificate if they do one of the following:
sign the birth register together
one parent completes a statutory declaration of parentage form and the other takes the signed form to register the birth
one parent goes to register the birth with a document from the court (for example, a court order) giving the father parental responsibility.
You can choose to register the birth on your own as you aren’t married to the child’s father. His details won’t be included on the birth certificate. It might however be possible to add the father’s details at a later date by completing an application for the re-registration of a child’s birth.
But if things do ever improve then your child does not need his name on a birth cert to know who her/his father is.
Your child has the right to a relationship with her/his dad. So you can invite ex to see the baby, ask him to occasions like christening, birthday, Christmas - not so much for him, but more for when the child's older, and asks about him. You can look her/him in the eye and honestly tell them you tried your hardest for their sake. If ex's family are willing to be part of your child's life it can work but if future grandchildren come along they may back off.
Your child also has a right to financial support. TBH whatever the ex's reaction it is the child's money, not yours, so claim it.