Those Huggies ads are such a joke!! They couldn't be further from reality. I had wanted to be pregnant for so long, and then I suffered SPD during the second 20wks. After doing three cycles of IVF and having an emergency c-sect, I felt guilty and inadequate. And for months after his birth, I seriously loathed the idea of being PG again. For a while the idea of having more children was abhorent to me.
I noticed that your DD is only 3months old. I don't mean to sound patronising, but perhaps with time you may change your mind? You never know. I know I feel differently now about being a SAHM and our plans for more children than I did 3 months ago.
Hopefully you can work out a balance that makes you happy!