I have previously had breast cancer. lately my right breast has become more enlarged and more heavy and fuller than the left, i also have pain in my right breast?

Breast cancer is usually painless to start with and that's why we miss it in early phase when the mass is still small unless it is detected by mammogram. You said you have breast cancer before but you did not say on what breast and what type of the first cancer. Some types have high risk of recurrence locally or in the opposite breast. Because of your history, you need to be evaluated by a doctor.