How after a setback do you stop spiralling yourself out of control. Cause I feel like I have nothing to lose almost after failing once then fail again so soon seems not as bad. Which is obviously very twisted thinking. 

This is the situation I found myself today, a big setback and just not being able to stop myself to watching p to the same extent as before.

I deff find this very hard.
Having a Mentor is a HUGE game changer for me.
I call him right after the fall.
Depending on what time of day it is that could be anywhere from a few minutes after to about 10 hours after.
Just knowing that I am going to be calling him helps me not fall again, partially cuz I'd rather say "Hey, I fell, what should I do/think" as opposed to "hey, I fell like 4 times... now what?"  
But also, because I know from the last few times I spoke to him, that I do have something to lose by falling again and that I'm not a lost cause, and that he will show me that, clearly,  when I call him.
He doesn't just give me cute chizuk "Get up and keep going", rather he knows me and knows what to say and how to say it to point out the truth of my struggles: "You made it X number of days/weeks (even hours) and you're gonna fall again cuz you fell once?! What's Shaichus?! Do you go say Loshon Hora again cuz you just said it already once? It's just the False guilt/'teshuva' feeling that the YH makes you think is making you give up. Don't do it! It's not you just because you fell again! You don't want this!"
I don't know if I'd be able to not fall again without a mentor, cuz as you pointed out: You know most of this already, you're just not caring then even though it makes logical sense.
Having a mentor is the best!
Hatzlacha in your Journey, we're all here for you!

See the The Battle of the Generation guardyoureyes.com/ebooks/item/the-battle-of-the-generation, chapters 10-11 (and Appendix A)

Dont let your fall identify who you are ,
meaning if you fall and now feel like garbage then you'll fall again cause your anyway a piece of garbage , but by focusing upwards and realizing the progress u made and btw the progress can even b that you m 1 time and not 3 or 4times is a sign that your shteiging and getting more control of the yitzrah dearayois.
      Good luck buddy !!! Were here for you