according to the symptoms told by you the possibilities are,
1.pregnancy as told by your gynecologist. If you are sure of dates still with negative pregnancy test, go for blood test
for pregnancy or transvaginal ultrasound
2. the cause for your symptoms may be galactorrhea
. Have you noticed any secretion coming from them when pressed.
Galactorrhea is a condition where milk secretion comes from the breast in lactating women.
In this condition also because of excessive prolactin absence of menstrual periods or delay in periods occur. Headache, vision loss
are symptoms when it occurs because of pituitary adenoma.
3.Other possibilities are mastitis(infection of breast), breast abscess
, adenoma of breast etc.
You have to consult surgeon and get examined.