When and how much flour do I add when mixing dough?
I'll convert my comment into an answer, based on your request for help or suggestions.  Bread formulas are created using the "Baker's Percentage Method".  It is expressed in the amount of liquid in ratio to the amount of flour.  This percentage varies according to the style of bread, but within each style produces accurate results when using weight measurement.  

Using volumetric measurement, especially for flour, is highly inaccurate because many variables can influence how much flour fits into a measuring cup (grind, humidity, compaction...etc).  That is why these kinds of recipes often suggest a range, and put the baker in the position of guessing.

Using a scale, and weighing your ingredients according to the baker's percentage of a recipe, removes the guess work.