Scottishmummy, your posts are horrible, I'm sorry. Do you have any idea what it's like to be spoken about in those terms? I don't care if you can quote evidence about them from here to eternity, Martha is first and foremost a HUMAN BEING who is in pain and suffering and the way you reduce it to clinical detail is not helping!
Martha you ARE valid. You also are NOT your illness.
My experience of Mother and Baby Units is this: the community team were much more full of all this crappy language about deterioration and disengagement and liking to sound full of themselves with their superior knowledge about mental health 
but on the ward itself they were nothing but caring and there WITH you and your baby. Safe. Warm. Nurturing. Seeing you and your pain as valid. Helping you to normalise all these fears that you have. Supporting you to get through the hard bits.
Generally, professionals who work intensively with people in pain are way better at talking about these things. They've seen it all and then some and they accept what is reality for you without talking to your illness... they will talk to you, not your symptoms.
I haven't had the elevated mood you have but I did crash very much after the birth. It was a really awful time and I remember it as being a bit of a blur. You really need people who get that. It is really hard for your partner to understand.
For some reason, women are more vulnerable on a second pregnancy - I think it's because of all the natural fears of what bringing another person into your house provokes in your illness. Your mind is trying to avoid these natural fears and because of that it is making you (paradoxically) much, much more ill.
You will be heard a lot more clearly on a Mother and Baby Unit. It's not what anyone wants at the start of pregnancy but it is the best place to go right now and it will give you what you MOST need... space to be seen, care for you that is sensitive for the fear that you feel, knowledge your baby will be cared for and you will be cared for. You can't see these positives now because you're seeing FROM your thoughts rather than being able to look AT your thoughts and see that you're just scared. This is making you very ill and it is unfortunately likely to make you a LOT more ill if you don't get help now.
I am thinking of you a lot. I really hope that you feel that you can get this help as soon as possible because I've been there and I know that you need it.
Hugs.