Re: I need an attitude adjustment!
Both of my kids wanted mama all the time. DD (now 6, also named Sierra) wouldn't eat any solids until about 11 months - she was 15 pounds at the time). DS (11.5 months) eats a couple tablespoons of baby food a day and some Gerber Finger Puffs - gets most of nutrition from nursing and he weighs 22 pounds. He usually nurses at least twice during the night and we have an extended nursing (about 45 minutes) right before bed. I nurse him frequently throughout the day.
Both of my kids also need a lot of physical contact (even DD still needs lots of snuggle time) and that did require an attitude adjustment for me - with DD I learned to accept that's what she needed and somehow I would get my mommy time without a kid attached in a sling or to the breast. DS has been the same way.
We don't cosleep (I can never sleep with a child/baby in the bed - no particular reason, I just can't), so I can't comment on that. Have you read the No Cry Sleep Solution? I think I remember reading some ideas about cosleeping in there.
I'm sorry I don't have any really good ideas for you. Keep your spirits up and you'll later remember these times fondly. They do grow so fast.