I understand your worries. But keep in mind that everything that helps genetic hair loss causes hair loss, including Rogaine, laser, hormone blocking medications. Anything and everything that works has a risk of shedding. Things that don't work don't cause shedding. I often advise patients that not doing anything also leads to hair falling out.
If it made your hair all fall out it wouldn't be used for hair loss! Some people describe mildly increased shedding for the first few months of using it regularly, but after that there should be a significant change for the better, with a positive net change to your hair.