Make fitting changes one at a time
A test garment helps separate fit problems from sewing problems. Use inexpensive cloth with a similar weight and stretch to your final fabric. Mark the waist and other reference lines so you can see whether the garment hangs level.
Try the garment on over the layers you expect to wear underneath. Pin one adjustment at a time and check both sides before trimming. Transfer successful changes to the paper pattern, including seam allowances and matching seam lengths. Keep notes for the next version.