Okay, I didn't bother reading all the responses so I'm sure I'll say a thing or two that has been said by everyone else. But I'm going to say it anyway.
I, too, have struggled with being overweight my whole life, and rejected. I, too, had a lot of one night stands and didn't feel attractive and felt worthless. It CAN be changed. I think the reason you do the "poor me" thing online and not in person is for a few reasons... "poor me" in person will just make people reject you to your face and that hurts, so you don't do it. "poor me" online is easier, you don't have to look at the person, and if they reject you, it's not as painful. People with "poor me" syndrome are just desiring attention. I am not a psychologist... but I've been told by several people that if there was just a big test you had to take to get your degree, I'd pass with flying colors. My psychologist told me I should be a psychologist!! So hopefully you'll try to take to heart some of what I'm going to say, despite the fact that I'm a complete stranger. First things first - you need to work on your self esteem. One thing I did that helped me with that was every morning when I woke up, I'd go look at myself in the mirror and say (out loud or in your head, doesn't matter...) all the things I liked about myself. Physically and otherwise. If a bad thought came into my head, I'd quickly dispel of it and continue trying to find the good things. Not always easy, but doable. And sometimes, you have to say things that you don't necessarily believe, but the things that other people keep telling you. Eventually you will believe it too. Also, find something you're good at and keep doing it. Self esteem builds when you're doing things on a daily basis that you don't feel like you failed at. Part of the reason you have a hard time meeting people is because of your negative attitude. Think about it... you see an attractive person at the bar, but they are sitting there, not smiling, all alone, shoulders slumped, and they reek of insecurity. Take the same attractive person sitting at the same bar, smiling, joking, laughing, and reeking of confidence... who are you more interested in?? If you have to pretend to have self esteem, then do it! Eventually it will feel real. You need to also deal with your past. Don't think about it on a daily basis, but schedule a time once or twice a week to just focus on that and how those events made you who you are today, and what can be done to change it. If you have anger towards certain people, write them a letter. That always helps me. Mail it if you want, or don't. Just getting the emotions out releases a lot of tension. I think as your self esteem gets better, some of the panic attack issues will go away as well. I, too, have suffered from panic attacks and still do on occasion, but they are getting less frequent. Here are some direct responses to the questions you asked at the end of your post...
Because you choose to be. Sounds stupid, right? But you do. Everything in life is a choice. How you handle what people say/do to you is a choice. Choose better. Choose to be happy. Choose to not be offended by the words people throw at you. Develop your self esteem. Do things you are good at. Enjoy life. Meditate. You'll be happier.
Why do I have no friends?
The answer to this is going to go hand in hand with your next question, which is why can't you get a date. Because people see you have no self esteem and that's a turn off. You seem needy. Constantly needing affirmation of how good of a person you are and how attractive you are. No one wants that. And I tell you... most people don't think this. It's instinct. They know they don't really like you, or you're not their type, but they don't necessarily know why right off the top of their heads. This is a big reason though.
Why do I struggle just make it through a day sometimes, while all the time appearing normal to everyone else?
Life is a struggle at times. But, same kinda thing I've been saying this whole time... become content and happy with who you are and it won't be such a struggle. You'll have more friends, more dates, more support.
Why do I keep saying things to people that consider me a friend that makes them not want to be my friend anymore?
This is more difficult to answer - depends on what kinds of things you are saying. If you are saying outright mean things, then it's because you have no self esteem and you try to belittle people to make yourself feel like the bigger better person. Is that what you meant?
Why is it the only reason I havent killled myself, thus far, is my incredible fear of what's on the other side of life?
Because there's a deeper reason. If you were meant to be dead, you would be by now, whether it was from suicide or something else. Seems to me like someone else deems you worthy to be on this planet. Someone bigger than you.
I hope that at least some of this was inspirational or eye opening or at least a bit of a help. Don't give up. That's the easy way out. If you need someone to talk to, feel free to PM me sometime. I think I'm a good listener. Just be prepared to sometimes hear things you don't necessarily like.
I'm not much of a sugar-coater. I, too, will recommend a book. It's called "Conversations with God" by Neale Donald Walsh. There are three books in the series. They are simply amazing. They helped me turn around my life. Along with my own determination.