Sorry if this is a repeat of things already posted, but I too wanted a child for the same reason as yourself.
All I can say is yes, it is hard, there are times I wish I could just have a switch to switch DD off with, however it is only DH and I, so we don't have breaks, we are either at work or with DD, although we do give each other time to themselves.
However, all I can say, is for years I felt like a nearly complete jigsaw puzzle (I've been with DH longer than I've not, so he is very much bonded and entwined within me iykwim), but I always knew there was a piece missing and nothing would have supplemented this piece. If this piece was never 'found' then I would have still been happy, but I would have felt incomplete. Once DD was born, the piece of jigsaw slotted into place. I now feel complete.
Oh, and where else can you get this type of conversation....
DH, Myself and DD in the car, DH and I belch at the same time and say pardon me.
DD starts to giggle and says, 'mummy, you and daddy burped at the same time.
Me: 'yes, I know, but we did say pardon'
DD: 'sometimes mummy, I cough and trump at the same time'
that is the piece of jigsaw that fulfils me.