partial hanging - help with knots please

[sweetbraid]

ive been trying to ctb via partial hanging, hanging on a (very very sturdy) doorknob in my bedroom. i start to lose consciousness and feel my breath get harder and then one of the knots loosens. im using an arbor knot on the doorknob and a slipknot around my neck. the slipknot is the one coming undone. any suggestions? should i use a different knot? thank you in advance

 

[Worndown]

DM.

 

[Microwave]

I'm also tinkering with partial hanging, from the hinge of a door,and would be interested to know how to make sure the slipknot doesn't come undone.