Please don't give up! I always have something go wrong with each quilt. I take is as a learning experience and go on from there. I have often made the same mistake more than once, several times in fact.
Maybe take a couple steps backward and make some really easy project to get your confidence back. Relearn the basics and you might find a step or two that you skipped at the beginning, thinking they weren't all that important at the time, or they didn't apply to what you were doing at the time. Now a couple of those beginner steps might make all the difference.
Use this board as a sounding board for each of your problems and I'm sure there will be 10 or 20 people with 10 or 20 different ideas on how to fix things.
Good luck!