Is it normal to find a tight knot on the side of one breast but not the other when you are about a week or so to your period?no other period symptoms.

Not unusual.: Hormones that control your periods also affect your breasts. If it feels like a definite lump but fluctuates routinely with your periods, it could be a benign condition such as a fibroadenoma or ectopic breast tissue. Based on your age and the fluctuation, this is probably benign. If it gets bigger, doesn't change with periods or if you have a family history of cancer, you should see a doctor.