I hear your anguish and I know it; I've cursed that same darkness myself and asked all those same questions. I've felt that terrible weariness that makes physical-based exhaustion look like child's play. It's a soul tiredness - a longing so profoundly deep and wide it's immeasurable; for the pain to cease, desist.
I'm sorry this has happened to you. I want you to know that you're NOT alone. I care. Other people on PC care.
Please don't be self-destructive and do things that will bring/cause you harm.
And love surely does exist, I guarantee you of that. And, no, I don't say this from the bosom of a loving relationship. I'm alone and lonely, terrified that I'll never "get it right" with somebody.
But I know that love exists. Sending you some now.