Sleeping on back help!

Any tips on getting my almost 3 week old daughter to sleep on her back? She's increasingly sleeping less and less on her back. Basically I'm up with her from 1:30-6am everyday because she'll only sleep while being held. I put her down to sleep & now she'll start crying after 5 minutes, then I start the process over again, nurse, rock to sleep, put down, repeat, swaddling doesn't work