Do chest exercises like pushups,chest press, dumbbell press, chest fly etc, consult a gym instructor for precise information.
Increase good quality protein in ur diet including soyabeans or soy based protein supplements. Soyabeans have phyto estrogens which help supplement body's natural levels of estrogens.
Take good quality fats from nuts n seeds like almonds, walnuts, chia seeds, flax Seeds, cod
liver oil etc.