Hi. I'm A Female Age 47; Weighing 127 Lbs. In

Hi. I'm a female age 47; weighing 127 lbs. In May 2016, I just stopped a 5 year regimen of Tamoxifen for DCIS stage 0. I gained almost 20 lbs since May. I eat very healthy.....no red meat, very little fat products. I exercise infrequently because of my work schedule and commute. I've never gained weight like this much before or this fast. Could my body be producing too much estrogen to fast?