My nine week old has reflux and is on prevacid (lansoprazole) but will only stay asleep for at most one hour, she only sleeps deeply when she is on me. is this safe?

Maybe: May have developed attachment and just manipulating you into holder them - normally reflux sleep best when head elevated - like in a carrier or maybe just when you are holding and their head is up. Enjoy snuggling, but try sitting in car carrier, etc to see if can wean. Hard to hold her and not have her slide off when you fall asleep.

Other suggestions: I would suggest elevating the head of her crib 30 degrees with a foam wedge placed under the mattress. Her room should be quiet and dimly lit with a night light or dark. The AAP guidelines recommend that she sleep on her back. Her crib may be placed near or in your room, to make feedings easier, but bright light and noise should be avoided.