How is sleep training with your baby?

My LO is 11 weeks almost 12 weeks, we start training her sleep her own in her crib since Monday. The first night she was cry a lot around 8:30-1am then got tired fall asleep. The next could days she cry less and less every day, she still can't sleep on her back ( cause she have bad reflux, she only can sleep on her tummy) so I will wait until she almost fall asleep put her on tummy then she will sleep till 8am. But last night she cry cry cry worst then pass few days, I almost give up cause she is really upset about stay in her crib. We have been training her 5 days and I can't see any happy ending is gonna happen soon....today she even don't want take any nap in her crib even 5 mins. We always make sure she is full, turn on the music and  clean diaper, not too cold or hot and we will stay with her the same room did i do something wrong? How long did you training your baby sleep ?