Estrogen has a growth promoting effect on breast tissue and also encourages water retention. These are part of its normal physiological function.
Depending what stage you are at, your body could be producing variable amounts of estrogen in the background in addition to what you are taking.
If switching application sites or reducing dose aren't suitable, other options include trying a different route such as patch or tablets, splitting your dose to apply a smaller amount twice a day rather than all at once, to smooth out fluctuations, or combining with a progestin with diuretic properties such as Slynd (drospirenone).
