HI DEAR THANKS FOR YOUR QUESTION.YOUR gaining weight along without taking too much of food,your breast size are increasing and your periods irregular,Dear all the symptoms you described points towards two clinical conditions No1;Hypothyroidism
and No 2; poly cystic ovarian disease
syndrome (POSD) .you should get your self investigated for both conditions.For hypothyroidism you have to do blood test
,called TSH.For POSD you get your get your ultrasound
and as well hormonal profile done and consult some gynecologist for further management.