First of all - DO NOT STOP QUILTING BECAUSE OF WAVY BORDERS!
Second of all - maybe you are just showing how clever you are. If any of us want wavy borders, we'd need you to show us how to do it. And why wouldn't we want wavy borders - they add dimension to your quilt!
Third of all - that's a gorgeous quilt that you can be proud of. So the border is a little wavy. Show me a quilt that's perfect and I'll show you a quilter who's a heck of a lot better than I am!
Lastly - be proud of what you have accomplished, consider the advice you get from this board, and on your third quilt just don't use a wide border. Problem solved.