That is generally a sign of engorgement. Breast Changes
As early as two weeks after conception, hormonal changes may make your breasts tender, tingly or sore, reports the Mayo Clinic. They may feel tender to the touch, fuller and heavier than usual. This is because of the rising levels of the hormone progesterone. The nipple area can also be extremely tender. You may notice the areola (darkened skin surrounding the nipple) seems darker in color and appears larger in size. Some women may also notice the appearance of Montgomery's tubercles, which are tiny "bumps" that are scattered on the areola. The use of a warm compress and a supportive bra may help minimize breast discomfort.

You need to see your doctor and make sure that you truly are pregnant and begin proper prenatal care.

Ooops... source: Livestrong.com.