After seven years, Laban switched wives on Jacob, so Jacob could not lie with Rachel until that time at least. It was a week later (Gen. 29:27-28). Next, Reuben is old enough to gather mandrakes. He has to be at last 5 or 6 years old; a woman can only get pregnant once every 10 months minimum. And now Leah has two more sons. We have accounted 8 years minimum for her.
Rachel would have taken a year or so to realize she was not bearing, and offer Bilbah. Three sons later is at least 4 more years (the maid needs to get new instructions each time). This accounts for 5 years or more here.
Jacob started building the speckled herd right after Rachel conceived. Building a sizeable herd would have taken at least three years or longer. We now have a total of at least 11 years, possibly more. Gen 31:41 counts 13 years since the day Jacob discovered it was Rachel. 7 to get children and 6 to get sheep.
Simple count: Year 7 of Jacob's stay, he gets Leah for a wife and then Rachel a week later. By year 12, Jacob has 5 kids by Leah, 3 by Bilbah, and none by Rachel. By year 14, Joseph is born, and Jacob starts working on the sheep thing. 6 years later, Joseph is 6 years old, Reuben is 12, and everyone leaves Laban.
