Life sucks for you right now, and anyone denying that is just completely devoid of understanding. Your pain is legitimate. It's okay to not know why you feel this way, it's okay to talk to people about it, and it's okay to cry when everything feels terrible. There's nothing wrong with you. 

It's not your fault if you feel awful, you didn't choose this. But, you do need to go and do things. Find the little things that make you happy and do them as often as possible. It's okay to be in a prison of pain and misery if you're trying to find a way out, but it's not okay to make that prison your home. Because when it becomes your home then their truly is no way out, and you begin to twistedly prefer the known pain to the unknown joy. We can try to help pull you out of this pit, but we can't help if you don't want to get out. 

You also need to understand that people love you and care about you. That there are people out there who might not know what you're dealing with, but would help if they knew. Hiding it from them doesn't do any good. Yes, some pain might be born out of rejection, but a lot of us will understand and try to help. So talk to us. Let us love you. You don't have to do this on your own. In fact, you shouldn't.