If you are using a paper pattern to cut around, are you maybe slicing off a little edge of the paper when you cut? I Used sand paper when I drew my pieces out , or you can cut a piece of stiff cardboard. I would get a straigth edge to start, then I would put the cardbosrd down, draw around it with as ballpoint pen, then lift the cardboard, and line it up perfect with the line I just drew., I would do this all the way across the fabric, then go back to the beginning and start over. I drew them all out bfore I cut any of them. Another thing you can do, make a second square the same exact size, and after yi have them cut out, check your fabric square with this to make sure it is square. When you are sewing, don't pull on your fabric, just guide it toward the needle. You don't want to stretch it. You still made a pretty quilt, and your colors look nice, and your seams seem to be matching pretty good until you get closer to that short side, that's why I wonder about your cutting pattern, and a few of the squares look as if you stretched them to match your seam. I'd suggest you slow down a little, and just try to have everything square and the same size seams and I think you weill do fine. I've been sewing more thasn 55 years, and today I ripped out forty short seams that I didn't get sewn straigh edge to edge, so everyone has bad days, we just have to keep trying to correct them as we go along. If you start getting off, on one, then it just gets worse the more you add. I hope maybe this helps you a little.