My breasts are swollen with blue veins that are very noticeable that are never there. and it's a week before my period. what could this be?

Pregnant: This is a common appearance of the breast with pregnancy, so check a test. Can also see it with anything that can cause breast enlargement (birth control pill use, weight gain, premenstrual breast swelling). Though it again is much more common with pregnancy.

Breast Veins: Blue veins around the nipple and on the breasts can increase with pregnancy but are not an indication of being pregnant. Veins on the breast can occur for many reasons including genetics, levels of hydration, body temperature and stress. These veins tend to be more prominent in fair skinned women and and usually a variations of normal findings.