Looks to me like your piecing is the cluprit. It is very difficult to get everything the correct size, especially when working with bias edges. Here is a site that I refer to to make my flying geese. They come out great every time. You still need to have the correct seam allowance. That is the key to all your piecing. Just think, if every seam is only a 1/16th off, that can easily add inches to the finished size. *Multiply each seam by this amount and you either get a piece that is too large or too small* I always use a scant 1/4th. To get this accurately, take a index card and sew your normal seam on the card. Now look at the lines and see where they line up against the sewing line. The sewing should be off 'just a little' and not exactly on the lines on the card. This is done because when we press our pieces to one side, it 'takes up' some of the threads. This is especially important with a quilt with lots of smaller pieces.
http://www.patchpieces.com/sharingpatch.html
OOPS! sorry this got so long. Quilting can be very frustrating at times. Just keep going. Use the 10 foot rule and all will be great!!