Velcro Baby

I am crying as i write this. My LO is 12 weeks and she constantly needs to be held. If she is awake she needs to be held upright and i need to be standing i should not sit. This has caused me immense back-pain. She stays in the play gym or bouncer for a max of 20 mins and then cries. We try to put her to sleep in the crib and she wakes up in 20 mins and needs to be held. We hired a nanny for this week and she contact naps the entire day on the nanny. In the evening she sticks to me and cries profusely if not held by me. She wont be even pacified by my husband. I cant pump due to this and need to stop whatever i am doing midway to make her stop crying. To put her to sleep
In the night i need to rock her aggravating my back pain. I am
Completely sleep deprived and frustrated. Please help and share suggestions if any.