L.F.
Do you have a swing? My dd had RSV when she was 4 months old and it took us 2 months to get her completely over it. Until then, every time we laid her on her back she couldn't breathe well. We ended up letting her sleep in her swing for almost the entire time. I asked her doctor if there was any problem with it and he said no, if it helps her feel comfortable, do it. You still have to snap her in, but it's not as difficult as the carrier is and I found that if she did wake up I would just start the swing and put the timer on for 15 minutes and she would drift right back off to sleep.
The only other thing I can think of to try is to put a t-shirt in the crib with her that you have been wearing or something else with your scent on it. I did this with my daughter as well and it seemed to comfort her greatly.
Good Luck!!