The ultasound showed the baby face down & normally the baby is facing up.(profile of baby is normally upward as of downward)

No, it's nothing to worry about. At 13 weeks, the baby is tiny, and is bouncing around in your uterus. It could be any way up or down. Trust me, that baby is going to do a lot of moving and bouncing and wiggling around in there before it comes out.

It doesn't mean anything. The baby will change positions frequently until about the 30th + week.