Nessy I really empathise with some of what you have said as I have spent all of my life saying I didn't ever want children. When I met my now DH, he had grown up assuming that one day he would get married and have a family but was not so wedded to the idea that he would give me up.
A couple of years into our marriage he got a bit more broody and we talked about it and I realised that him giving up the idea of being a parent was a much bigger deal (for us) than me not having children. I like children, have many siblings, neices, nephews etc and quite a few of my friends are parents. I'd always focussed on my career and thought children wouldn't fit, but now think we can manage that.
Anyway, went off track and very mememe there so apologies.
The bit I recognised was not wanting to talk to people because of the embarrassment of changing your mind. If I'm totally honest, I was also annoyed at proving the people right who had always said I would change my mind (as I had, at the time, been annoyed that they thought they knew my mind better than I did
)
Even now we are TTCing I've not really talked to many people (other than DH) but then we're on the same page. In your situation I would want to talk to DH in a reasoned way to explain you thought one way and now realise that you feel differently. It will be a shock for him and take some getting used to (it took my DH a while to get his head round my change of heart and he had originally wanted it!) One of the deciding factors for me was envisioning my life in 5 or 10 years time, being too old to make the decision then (devil's advocate) and realising I would hate it.
I think when we finally get to the stage when we have a pregnancy to announce, there will be some shocked faces.
I will just add one final thought, that on here I have found some fabulous and like-minded ladies to chat to and have shared things that I would never dream of talking to some real life friends about. The anonymity means you can really open up and also, it's great to meet people who have experienced things you can learn from.
Good luck