Are you stretching the fabric as you're sewing? I would use a cotton batting and when you quilt it and shrink it up, I think you'll like it better.

Before borders~
lay quilt out flat
measure across the quilt in 3 areas, top, middle and bottom.
lets say it is 50-51-52 inches
I would cut 2 borders out at 51" (average of the 3 measurements)
pin and sew.
Repeat the same on the next border... should help square up a quilt.

As a quilter, I would take the borders off and fix it. I have seen where there were 9" of extra border in a quilt.
Quilting this out is hard with out pleating the quilt.

I am pretty sure "You can quilt that OUT!!!!!!!!!!!!! I think it is beautiful.

I am no expert, by any means, but I am guessing it could be the mitered corners. If you flatten it out with your hand where do most of the waves seem to be? Near the corners or all along? If you can play with it and figure out a way to adjust the corners that might help. Use that seam riper and try again.

I think it looks better than you think, but I can see a ripple in the bottom border. Did you measure the top, middle and bottom & divide by 3? That is how I was taught. I would rip out the bottom border, remeasure it and cut off the extra (it only appears to be an inch or so) and sew it back on. Its a very pretty quilt and don't give up on quilting.

I see it. Hmmm....

First, when you have busy fabrics in the border, just do a straight border. No one is ever going to notice that you worked so hard! Save that effort for when it will show.

If you measured before you sewed, make sure you use lots of pins. I mark, with pins, where the middle and quarter points are on both the base of the quilt and on the border. I put the base of the quilt with the border and match up the pins. I add more pins in between. If there is some fullness in either the base or the border I try to keep it where it is - don't move the fullness somewhere else.

Now, if all that didn't work, I'm going to swear you to secrecy:

Try starch, sizing or Best Press. Soak the offending area, and use an iron to press it into submission.

After that, you'll want to 'quilt to death' that border. It will suck up extra fabric and keep it where you want it. Piano keys and bead board (piano key with two line about 1/4" away from each other) also help suck up extra fabric and look great on busy fabrics. If you try to do just a little bit of quilting, it will look lumpy after it is washed, so quilt it down!

Once you're done, the quilt will look great. Make sure you let us know if these tricks work for you, and SHHHHH!!!!

HTH!!

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.

Shelley gave you excellent advice! I have found that mitered borders have a tendency to be wavier then the straight borders, but not always! I agree with Shelley though, you can quilt that out with heavy quilting in the borders. Can't wait to see what you do with it!

other than taking them off and remeasuring and resewing them on, you could take the seam out from the center toward the corners till you come to areas that are not wavy, then take a seam in the center to make it fit. then resew back on.
usually you measure the quilt top in the middle-that will be the measurement of the top and bottom borders. then later measure the length down the center, that will be the measurements of the side borders. just add seam allowances. place the borders on, matching centers and corners and pin. then sew.