Not sure which method you'r using for making HST's, but if you're attempting to get there by sewing two small triangles together, there's better ways. The 2 at a time method would help. Someone mentioned the 8 at a time technique. I use the strip tube technique and it produces perfect HST's every time. No squaring up after the fact either.
Also, there's no need to start your stitching right on the raw edge. As long as you start your stitching somewhere within what will be a seam allowance, you'll be good.
Hope we see more of you other than your first/only post.