Hey Tiger! I am a NewB too and had some problems like you are. Stability is a major part of Level 3 ( I am assuming that is the level you are on) Remember that a good arch consists of 3 parts; Big arms, hips down, and positive legs. I had problems with keeping that air pressure on my legs. I would practice in the living room on the floor with my toes on the couch. I hope this helps! Good Luck!
JAMES