The short and narrow is that your parents sound like completely neglectful pieces of shit who didn't give you much guidance, or arm you with the tools and knowledge to tackle life. I guess you can console yourself with that fact, because really it's not entirely your fault. You can place a lot of blame on your parents when you've come to adulthood being as big an idiot as you are. (And take my word for it, you're a fucking idiot, by pretty much every definition of the word.)
But that's the bad news... on to the good news -
You seems fairly intelligent and aware with a decent enough capability of self-analyzation, so you aren't a totally lost cause, even though your situation may make you feel like you are. Since you're capable of looking at yourself and recognizing your shortcomings, you should be capable of changing those things you don't like about yourself. Thanks to your parents neglect of you and their failure to teach you good judgment, failure to teach you how "things get done" and how to "follow through" and all that jazz, you have a long journey ahead of you to change the handicaps they left you with. It's gonna be long, frustrating, confusing, and dispiriting, and most likely you're going to make other poor judgments and bad decisions along the way, but if you're vigilant about changing yourself, if you put your mind to it enough, you'll learn from each of your mistakes and you'll learn how to avoid mistakes in the future. Here's some things that might help -
Change starts from within.
Any change to your exterior world begins from within. If jobs haven't worked out the way you wanted them to, or past decisions are hampering you, (etc etc), the first step in changing your environment and situation is to look inside yourself and identify WHO EXACTLY IT IS YOU WANT TO BE. Whether it's corporate chairman or Al the shoe shiner, you have to decide who and what kind or person you want to be. And like a sculptor chipping away at a block of stone, you need to remove from your personality those habits, attributes, attitudes, learned behaviors, or instincts that hamper your goal of becoming that person. It ain't brain surgery. If you want to be a corporate head, (for example), staying up until 4am and sleeping til noon ain't exactly a habit you want to encourage in yourself, right? Well... as the sculptor of your own destiny, better remove that piece from your personality if you're serious about becoming that person. Same concept applies to the personality trait you said you have, which is pussyitis. If you actually intend on changing your life, growing a spine is pretty much a prerequisite. You might have difficulty at first doing it, but standing up for yourself and getting out of your shell eventually gets easier and easier. So even if you kind of suck at it at first, keep mentally vigilant of the fact that you need to assert yourself more and not be anyone's doormat. Eventually it will become a natural thing to do and you won't have to think about it anymore. Apply that same concept to anything - personal change and growth comes slow, but it gets easier every single time, to the point where eventually you wont even realize you're doing it.
It ain't ALL about you
There's a whole world out there dude. It's vast. It's filled with cool shit. It's filled with horrible shit. It's electrifying and terrifying and stimulating and frustrating. There's enough stuff in the world to keep you mesmerized and interested for the next 10 thousand years. So don't dwell on yourself and your own little world all the time, even if you are trying to change your world from within. Start looking around you. READ THINGS. Find out how things work. Find out why people do what they do. Read autobiographies of successful people and take away their perspectives. Basically - get outta your own head and jump in the mix and learn about the world around you. Meaningless information comes in handy in the oddest of circumstances, and maybe if you had read a book or two, you might have thought ahead to cover your ass when it came to the dumb admissions bitch putting you into the trick bag at school. (For example)
Be realistic
You, and your situation, aren't going to change overnight. There's a long road ahead of you before things are going to be what you're satisfied with. Along that road you're gonna have to simply settle for stepping stones. Put a goal in mind, whether it's getting back into school or saving enough money or whatever else, AND DO WHATEVER THE FUCK IT TAKES TO GET THERE. Take jobs you don't necessarily WANT to work if there's more pay involved, or if it will teach you a skill you can use to push yourself further. Personally, judging from what little I know based on what you've said in this thread, I seriously suggest you get yourself enrolled in a trucking school. Is trucking a glamorous job? No. Do people look down on it and thumb their nose at it? Yep. But fuck 'em. They aren't walking in your shoes and you're the one who has to live with your reality. Truck driving is one of the few jobs in America any man can get and make a decent wage from. Also, it gives a lot of time to think and self-reflect, and there isn't too much dealing with other people. On top of it all, you get to travel around and get out of mom's basement and your crime-ridden neighborhood, plus learn a lot of how the world works. You aren't too life-experienced yet and you don't seem to know much about "how things work" in the world, and if there's one thing truck driving will teach you, it's how things work. You'll have to think for yourself in a lot of situations, but at the same time, if worse comes to worst you can always call home to your dispatcher and ask for advice or assistance. So... unlike the military... you can get life experience, a decent paycheck, travel and adventure, all without some fuckhead screaming in your face or making you run in hundred degree weather, etc. It ain't a glamorous job, but it pays the bills and it's something you can do without a formal education. Sell that fuckin bike, save up some cash, and go to a trucking school. Hell, Schneider used to even train drivers for free if you signed a contract to drive with them, explore that route. Even if you hate trucking, do it anyway. Get the experience. There's quite a few drivers who pull down pretty decent livings, or have used the class A certification to move on to other equipment, cranes, earth movers, etc. And they make a pretty decent wage.
Anyway, that's my advice.
