Sounds like you just need to practice more. I had the same problems starting out. Then one day it all looked good! Are you pulling your bobbin thread up? That is usually the cause of birds nests I think. One thing that made me feel better when I first started was to match the thread color on the back. Mistakes were less noticeable. Don't forget, most people won't see the mistakes that you see. Keep the machine speed faster and your hands slower.
Keep practicing, it will get better!