I'm sorry to hear things are as rough and out of control as that. By the sound of it, things possibly get worse when you're under stress.
I used to have fits of rage myself that involved breaking things and so on.
One of the things that helped me stop was that I eventually realized that the rage/anxiety was linked to a feeling of helplessness. I couldn't think of any healthy ways of getting what I wanted or of expressing my feelings (and I was ironically afraid of doing so... and I also didn't think anybody would care) so the rage would just build up over time and get triggered by little things.
I don't know if this could be the case for you but in my case I only ever had two modes back then: A) meek and submissive, B) raging and out of control.
Basically what I wanted to be, and what I felt I ought to be; was meek and submissive and so the only way in which the parts of me that wanted to get their way (or assert themselves or even just express themselves) could get what they wanted - was by making me lose control.
Another thing that helped was developing an awareness as to what was really bothering me at any point in time. This is, of course, a lot easier said than done with BPD and it usually takes a while… but at any rate, the self awareness is what helped me realize what was really bothering me whenever I felt triggered… usually the cause wasn't the trigger itself but the stress or tension that had been building up, up until that point.
I should note though that the anger over the trigger wasn't always 100% irrational because a trigger is usually something that in some way reminds us of the true cause of our anger/anxiety/pain. Examining what caused it to be a trigger can sometimes lead us to understand the true cause of the pain.
For example, if what triggered you was your gf wanting to go to bed early, that might imply that there's something in your relationship with her that makes you feel uneasy and might need to be addressed. Then again, the problem might not be with the specific relationship with your gf per ce but with relationships in general (as is often the case for us)… but that too is also something that needs to be examined and addressed… and this of course requires self awareness.
Another thing that helped was that I became aware of the pattern of catastrophic thinking that kept leading me down that path time and time again. In a way it was like an inner demon that seemed to want to lead me down the path of destruction/self destruction and would say anything it could think of in order to lead me down that path, regardless of the circumstances. Eventually I learned to talk back to it and say things like "oh yeah? Life is over? I have no other choice but do X? Well that's what you said last time and the time before that and the time before that and you were always wrong!".
And finally, one of the big things that helped (and I hope this won't be triggering) was that one day I told myself that I "don't want to 'be' the kind of person that can only deal with problems by having fits of rage". I wanted to be the one in control and not let anything else, even from within, have that kind of control over my life.
I hope any of this can help… and good luck; I know how hellish rage can be, even if it doesn't seem that way to people from the outside.
Gratitude can heal most wounds.
(What can I say… I don't like the word "all")