Guild Wars 2

Not sure if this is bug ,but while in the form i loose my astral force prematureli while taking high damage often happened that i end up on zero after 1-2 seconds.
Seems like astral fore working like additional healt pool due to it i cant simply keep on it while under constant attack i lose it all in seconds.
There is also no mention about it in description of skill. I Will be glad if someone can help me with it or if im something missing.

sorry for my english.

cant buy anything buy tab is still greyed out:(