Daniella, Its not to good to be laying down to much, i realize that your in pain,
but not getting blood circulation going is not good, as Dahlek said.

I use to go down to my local swimming pool and just walk up and down the lanes, go as slow as you like, its great cardio exercise and the best part is its non weight being so you won't hurt like trying to walk on hard surfaces.

I found that if i got to the pool early for me it was 6.00 am and there were lots of people doing the same thing for all differant medical problems.
Even a 15 minute walk in the pool to start with is a lot better than nothing, then you can build up longer times as you feel you can do it.

good luck anyway
Brian