Your quilt is beautiful and I really can't see the problem that you don't like.
The only thing I can think of in addition to the ones others wrote about is:
It looks like you are sewing over a seam line where the seam is pressed toward the point of your needle, this maybe raising the tip of your presser foot a little, you might try using a small piece of folded fabric under the base of the presser food to level it out. This works with heavy fabric but I have not really noticed a problem with thin matterial.