When im going to sleep this feeling starts to build up that im going to apprach a ugly full hard stop dukkha cessation, this really freaks me out, been without sleeping for 3 days. What should i do?

Didn´t achieve path yet, but was mainly trying to do it with the impermanence door. In high equanimity/formations right now.

The lack of sleep is starting to make a toil on my mental health

Go to sleep,
You have no idea what will happen, so its all bullshit that you are making up. Get over your Knowledge of Fear and stop worrying until something real happens. Not that fear ain't real, because it is, but you didn't ask about that.
~D

Are you still meditating? Maybe you should stop for a while, or try a different technique (more samatha and less vipassana)?

This dukkha cessation is called "sleep"
You should try it some time... and I would even add ASAP
But maybe you want to destroy your body and mind. Who knows. People have different goals. I do not judge