Left breast feels bruised, female 28years old. not on any tablets or contraceptive. not breast feeding. what could be causing this dull ache? thankyou

Mastalgia: Breast pain or mastalgia is usually described as a dull ache. It can be cyclical and a response to hormonal changes or non cyclical and without known cause. When in doubt, a good breast exam can be reassuring. Hormonal pain tends to be both sides and on the outer aspect, not associated with lumps or cysts, and lasts about 5-7 days a month.