I don't know exactly how you feel, but I know the feeling of loneliness well – it's a terrible, crippling feeling.
My situation is similar to yours in some regards. I've been trying to figure-out a direction to take my life in since finishing school, and I've been drowning in free-time. At first, I'd spend all that time consumed by rumination, and that just amplified everything that's negative and made me feel more isolated.
It sounds to me like you do want to get over this, and you've even taken action to try and make positive strides but things don't seem to be getting better, and that's discouraging and demoralizing. However, you can't give-up, not when you've seemingly got fight left in you.
It's very important that you recognize and appreciate that fact about yourself, because it's key. Half the battle is that willingness to fight and try, and you should celebrate that about yourself. Seriously.
You asked why you would have zero friends, and it sounds like you've concluded that it's because you're not an easy person to get along with, but I disagree. Sure, I don't know anything about you or your personality, but I think you're doing a great dis-service to yourself by beating yourself up with that sentiment. It's tough in our world today to maintain meaningful relationships. Everything is moving so fast, and the world demands more of us. On top of that we don't connect in person as much as we do virtually. It all compounds to make it that much harder to meet people and build relationships. So that might be why you have zero friends as you say, and again going back to my previous point even if there is truth to your self-critic it's incredibly admirable that you're working to fix it.
Anyway, just wanted to leave a brief message to let you know that in this small way at least you aren't alone, and if you keep fighting you will eventually get to where you want to be. If you'd like to talk more PM – I hope you get through this!