Oaioaad heaviness of upper and right side of right breast two weeks before period then stops during period. what is this?

Estrogen : Effects . Why it is bothering your riff her breast more than the left is not so clear but probably related to where the receptors are

Hormones: Breast tenderness can be normal before your menses, however, it should not be distressingly uncomfortable. Try limiting stimulants like caffeine and nicotine and add vitamin E during that time. This will also help if you have fibrous breasts.