Help?

M.J.
My LO is 8 weeks and she absolutely HATES laying down flat. It's been like that since the day she was born. She absolutely will not lay in a crib, pack in play or even next to me in a bed. She will only sleep in my arms sitting up or in her rock and play sleeper by fisher price which, is at an incline up to 25 lbs. She is currently 12 lbs and I have a little while before she reaches the weight limit but I am trying to figure out how to transition her to sleep in something that is not inclined? Any advice will be greatly appreciated. TIA