I am stuck in swtraight line mode on all pens and brushes. How do I access a free form line?
What platform are you using? iPad, Windows? And what stylus?
On the iPad, there is a setting under "Input" in the "Touch" section, for "snapline" = this setting snaps a line to straight line if you hold at the end of a stroke. Is this what you're seeing?
Do you have the ruler tool turned on?
Another way to force straight lines is to enable perspective grid from the toolpar on the right.