How early have some women reported having pregnancy symptoms?

My breast are sore and I'm only 9dpo. I've never had sore breasts before menstration...could this be an early pregnancy symptom?
How early have some women reported having pregnancy symptoms?

Most common on 9 days past ovulation with 12.4% of pregnant women experiencing it.

Changes to your breasts can begin very soon after conception. This might be your first clue that you are pregnant! Increasing levels of hormones cause increased blood flow and changes to the breast tissue. As milk ducts and milk-producing cells develop your breasts may feel swollen, tender or very sensitive to touch. You may also feel throbbing, burning sensation or itchiness. Your breasts may also grow in size, feel heavy or change in shape.