Welcome @Dandelion. If they're planning on rads they tend to over-expand the tissue expander so if the skin shrinks a bit after rads it will be fine for the new softees. It took about 6 weeks for me to get used to my tissue expanders and I found a little neck pillow positioned under my side and allowing the boob through the hole allowed me to sleep on my side. ..also hugging a flat pillow and 1 behind my back. Once I could do this I finally slept through. I've had my expanders in 14 months and am used to them now. Hoping you won't have them as long.
Osteopenia is low bone but not low enough to be osteoporosis. Something to be watched when you go on hormone blockers. You'll have yearly bone mineral density scans I would imagin
Hope this helps. Kath x