Celine Dion is currently building her strength after going through a rough patch regarding her health, but a new video has revealed how she struggled with getting back into the recording booth after giving birth to her son.MORE: Celine Dion out of the spotlight - details on her return amid health concerns"When I started to sing again professionally, I wanted to make sure a couple of days before that I was going to be in shape," she revealed in her latest post, taken from a behind-the-scenes documentary from 2002.WATCH: Celine Dion surprises fans with exciting announcementThe special showed moments from the making of her then comeback album, A New Day Has Come, the first she'd made since giving birth to her eldest son. Showing off some of her vocal exercises, she continued: "And the first few times I was like 'ooh okay', my voice wasn't as flexible and stretchy.