Life has handed you a very hard time, an appalling childhood, bad relationships, the separation from your brother and more recently the death of your best friend. Plus of course your mum finding someone she is interested in, all of this leaving you alone.
Actually I rather admire you, to be able to cope at all with these things all piling up is an indication of the strength inside you. I'm not suggesting it is anything other than terrible, but somehow you have survived.
You are, if like me, full of painful feelings and it is only human when in that state to want to talk to others -to vent, to seek comfort, to have companionship. Sadly it is the time when you find out who will really try on your behalf.
When my first partner died I wanted to die too, and talked needlessly of my pain. Very quickly everyone else -having offered token sympathy and suggested totally unrealistic options - or told me to "move on" (a phrase I hate).
I was left with one who patiently listened and did not try to fix the situation. In that I was very lucky, such people are rare gold, and if that person had not existed I'd have had to try and navigate my life alone.
May I suggest that some of that anger and resentment (which I felt too) may not always be deserved. Some time later one of my so called friends did make contact and and admitted they'd avoided me, as they felt bad, had no answers and felt guilty as a result.
Many people simply do not have the life skills to respond. I think you would be one of the ones with those hard-won skills and a good person to go to -a rare person.
I'm sure you know some partial remedies, to try new ventures that you might enjoy, things where you meet others, where you gain satisfaction and nudge life back towards the bearable. I can't suggest what they might be for you, anything from volunteering at a museum to the gym to walking dogs from the pound.
As you meet other people maybe it is not a time to seek their sympathy -that has not worked, but instead try to make their meetings with you enjoyable -so they look forward to them again. Yes, I know, hard when you feel so bad inside.
You have been wise enough to come here, and can say what you wish - you will always be welcome