can lack of estrogen make you fatigued?

I've had to get more physically active for PT the last 3 months or so and dropped about 6- 8 lbs. with all their exercises daily, twice a day and walking. I am also more fatigued.
My breasts are flappier, saggier, less body fat. but can't seem to keep estrogen up....... I do use bioidentical hormones.
any thoughts?
My theory on this is that I lost some estrogen from being more physically active a nd lost some fat that estrogen was stored in. and I can't seem to gain it back.... staying the same . went from 136 to 129 to 130 lbs.
?