Are you standing in your ski boot trying to flex it, or are you literally just pushing on it with your hands?
Flex isn't about how good of a skier you are or what kind of skiing you do. It is primarily based on your weight and ankle flexibility.
Next time you have a boot issue, we made a boot-fitting thread so please put your questions there and be sure to read through it, since we have answered this question already. It will be a good resource for you to use down the road.