Hi Shirley,
Firstly I assume that you have applied paste liberally to the paper AND the ceiling (apply to ceiling just before you stick each piece of paper up).
If so, then your problem is putting filler in the gap between the paper. This should NOT be done. A couple of coats of paint will fill this gap.
A tip:
Try painting the seams with a brush first, letting it dry and THEN roller the entire ceiling.
Kind regards
The Building Sheriff.
The Building sheriff (www.buildingsheriff.com), September 2010