It is difficult to pinpoint the main cause of breast pain, but it may be due to one or a combination of these factors:

*.Hormonal changes-
Changes in reproductive hormone levels are strongly related to the menstrual cycle. These in turn coincide with the occurrence of breast pain which may disappear or decrease when the woman gets pregnant or undergoes menopause. However, there are no studies which have linked these hormonal changes to breast pain.

*.Anatomical changes-
Noncyclic pain in the breast may occur as a result of anatomical factors like breast trauma, breast surgery, breast cysts, or other localized changes in the breast.
This type of breast pain can also originate from the chest muscles, joints or the heart, and can radiate to one breast.

*.Imbalance in fatty acids-
Another theory proposes that the breast tissues are sensitive to hormonal levels which are affected by imbalances in fatty acid levels.
This is the reason why some women use evening primrose oil, a source of gamma-linolenic acid (a fatty acid).
It is believed to reduce breast tissue sensitivity to hormones by restoring balance in fatty acid levels.

*.Effect of medications-
Hormonal medications like oral contraceptives, infertility medications and hormonal therapy for menopause can cause breast pain. Other medications that can affect the breasts include antidepressants like sertraline (Zoloft) and fluoxetine (Prozac).

*.Large breasts-
Breast size can bring about constant breast pain that may be accompanied by discomfort in the neck and shoulders, as well as back pain. These may be relieved by breast size reduction.

http://afolabibayor..com/2017/05/why-do-my-breasts-hurt.html?spref=tw

Cc
Lalasticlala
Ishilove
Semid4lyfe
Obinoscopy
mynd44

In case you missed this:
What If One Of My Breasts Is Bigger Than The Other?

http://afolabibayor..com/2017/03/what-if-one-of-my-breasts-is-bigger.html?spref=tw

OK. I'm coming

It's too heavy. I think it needs some bf attention ASAP.

Cool

Well, Op highlighted common causes of breast pain involving both breasts.
In the eventuality of one sided breast pain, it could possibly be a sign of early onset infection, trauma from sleeping position, excessive handling, or even vigorous sucking.
And in extremes of cases, esp in the middle age to elderly women, it could be a warning sign of something more serious like breast mass or early onset cancer.
If pain isn't taken care of with normal painkillers, biko visit the hospital.