hesmy1nonly welcome to the forum
I am sorry to hear about your family and mostly about your 3-year old cousin
For the most part breast cancer is without pain - that's why it is so dangerous if not regularly checked.
Although I strongly advise you to see a doctor as soon as possible, I rather think you are having a hormonal disruption of kinds.... this because your nauesousisness and change in menstrual periods.
Still: you need to see a doctor. Only with tests can he discover what is the problem
Feel good