Hi BlueJustine,
I can relate to a lot of what you say here but don't despair because there is a way out. However, you need to take a deep breath, calm down and stand back a bit. The way forward will not necessarily be easy as it need some hard work from you and you need to be blunt with yourself.
First off, you need to dump all that negative crap about yourself. Repeat a hundred times 'I am not a loser'! Now write it down a hundred times! Repeat every time this negative thought comes into your head. Again you must drop all this bitterness. Take a step back and ask yourself a simple question: would YOU want to be friends with YOU? It may not seem like it but those people who 'get on your nerves' could be your salvation. The American essayist Ralph Waldo Emerson said, 'The only way to have a friend is to be one'. This is so true, believe me, and I think could be the key to your recovery as it was mine. Talk to someone, smile at people, ask them about what THEY feel - about anything, the weather, last night's TV, their favourite sport (even if you can't abide it). Build up a connection with someone by revealing little secrets about yourself. That will prompt them to reveal little things about themselves in return. Help someone else in small ways, buy them a coffee or something. What I am getting at is stop thinking of yourself and think of others instead. It may not seem like it but most people have times of self-doubt, few have the complete confidence they sometimes radiate.
So what about it? Dump all that negative stuff and think positive. You can't alter the past but you can shape the future. Prople may laugh to see a change in you but remember that nothing good has ever been achieved without people laughing at the outset. Ignore them. The time is yours in which to make amends in. Good luck!