Sudden Extreme lag in premiere pro

Hello !

I have really anoying lag on premiere that came all of a sudden. 
I am edditintg 4k at different framerates from different camera with rezised fx to match a 1080p sequence. so yes the edit process is heavy. But i've been editing for several weeks on the same project with the same footages and it has been flawless. So i know my computer can handle this pretty well. But two days ago it became just impossible to continue to work on that same projetct. Everytime i want to lauch a playack it takes sometimes up to 10s to actually play the video. and when i do trim or edit anything (even sound) and i try move my playhead to check the modidication i made, then it is now minutes i have to wait while Premiere "is not responding"'. 
I have allready cleared cache, made sure it is in the right place, render, mute fx, update my Nvidia graphic card, duplicate the project, open a new project and import the sequence on it... Windiows and adobe PP are on the laster version... and it is still unusable. Not just anoying, unusable ! 
Sincerly thinking on switching to another soft beacause this is not the first time weird things like that had happen on Premiere. Hopefuly it is not a paid work because i would be in so much trouble right now.
In the meantime if someone can get me out of this nightmare so i can at least finish the editing on this project it would be really kind 😃