Free cash is showing negative

i have shorts on nifty and things have gone bad… But my free cash has moved to negative even though my loses are not as huge as margin that was already blocked before… Now i would like to buy puts but I can’t and it says I need more margin. When I checked it showed i had negative cash… Is the margin blocked increases if our position moves to loss? How !much money will be blocked for 100 points move in nifty against our position?