Hi Bec,
I felt I had to respond as what you wrote resonates a lot with my own experience. Like you I had quite a good sex life before baby and now with a 9 months daughter is all gone.
Last week I finally picked up the phone to a PND helpline and they have rightly told me (after listening) to book an appt with my GP. I was surprised to see myself cry over the phone to them and this morning againg at my GP's.
I too feel that I've been putting on a brave front for too long and then it all came down on me... I really want to change this and get back to my own self.
You might be thinking it's nothing major and that you are kind of ok but you might struggle to do things. I'm mostly fine in term of caring for my daughter but struggle with house chores, work and find that I get emotional at anything.
If GP is not good for you speak to someone else: health visitor, friend, partner, relative. Find just one person to 'come out' to start the process of feeling better.
Hope this is helping somehow! xxx