Flat oatmeal raisin cookies?

I make oatmeal raisin cookies a lot, and everybody loves them. They are chewy and soft, but they're so FLAT! I usually add another 1/4-1/2 cup of flour since the dough gets very sticky, and otherwise I follow the recipe exactly. Just bought new baking soda, so I know old/inactive baking soda isn't the problem.

Can I add an extra teaspoon of baking soda to the batter, or will that ruin it?

Any other suggestions?

did you use yeast, that could help or just use more baking soda