Don't forget, even guys who were always skinny start to put on weight as they get older.
Also, women can be very thin if they they take care of themselves. So even if estrogen is causing you to put on the weight, eating better and working out would take care of that.
Don't start taking something to control estrogen without the advice of several good doctors! Taking finasteride alters your hormones somewhat... not that good in concept but its been proven to be pretty safe over decades of use for the prostate.
Taking something else to try to balance it out with be TRULY messing with your hormones.
MH