Heavy Depression

Although I'd rather not kick off my introduction to this seemingly wonderful site with a personal dose of my own negativity, I'm going to anyways.
I'd prefer to not feel this way, but I'm struggling right now so here goes:
I may or may not have BPD. That makes it very hard to just make it through each day. It's an uphill battle and I'm almost always losing. I also deal with psychotic tendencies on occasion. Just thought I'd throw that out there but I will attempt to suppress them the best I can while online.
Over time I've lost many friends, my sanity on and off and even my cat that I loved like a little brother.
Recently I find that I'm dealing with reoccurring loneliness and depression even several months after losing a girl that I considered to be a true friend and had a special connection with.
I feel like my personality makes it impossible to keep anyone around as I have a knack for pissing others off sometimes without even trying. 

I have helped several people over the last few years ever since I almost attempted suicide and promised to never fall so far again. I am somewhat of a martyr as I will put other people's suffering before my own needs and do whatever I can to pull them off that ledge so to speak. However, I have another side to me that is truly sadistic. I'm struggling to let go of this darkness but I'm addicted and it ruins the possibility of having a relationship or forming a close friendship with someone.

Truly I just don't know what to do anymore..

Try not to harm yourself; don't harm anybody else; don't make things worse; get through the day; get through tomorrow.
And do not make any big decisions while you're still in depression.

Truly I just don't know what to do anymore..  

Then don't do anything. What can you even do? 
You know that nothing works. No action you take is working. Then turn towards no-doing. Become a watcher rather than a doer. 
Mind is great as a slave or utility, but very dangerous as a master. Really, you can't do much because the cure doesn't lie in doing something, but in no-doing. 

Take darkness for example. Darkness is not an entity of its own, but it is an absence, absence of light. And you know that you cannot do something directly on something that doesn't exist. You bring the light in, and darkness disappears. You do something with the light, not darkness. Darkness leaves on its own. 

Loneliness, depression are not an existence of their own. They are absences of something. Depression is lack/absence of expression. Loneliness is the absence of solitude, which is simply the realization of your aloneness. 
You don't do anything to depression, but be more expressive, and depression will cease.