Hi New sport:  You're certainly doing all the right things for exercise and supplements so I really hope that helps your bone density.  You didn't mention your t-scores, so I was wondering what your Dr thinks about the gymnastics/jumping.  This is just my opinion and that of the NOF (National Osteoporosis Foundation) but jumping with low bone density (low t-scores) *can* be potentially dangerous, because it puts too much external force on your spine/hip/joints in a very jarring way.

I've had many spinal frax's so I know I personally couldn't do any jumping, but you'll have to decide this for yourself; I would just be really careful and talk to your Dr or Physical therapist about doing this particular exercise.

You are correct that long-term use of bisphosphonates may cause brittle bones in some, but the main thing that was reported in all the studies I've read on this topic is the long-term use of these drugs in relation to this problem.  I don't know if there have been any studies on those who took these meds for a limited time, and then took a drug holiday, that experienced the brittle bone effect.  Also, this phenomenom does not happen in all those taking the medication, but it has happened in some, so there's no gaurantee that it will happen to you, but I can see why it would be of concern.

Have you considered Forteo?  You may have objections with this med as well, but it doesn't have the same effect that bisphosphonates do, and it doesn't cause brittle bone.  Forteo is the only med I know of that works both on bone resorption and formation.  It's often used in conjunction with broken bones to speed healing as well because of it's effect on new bone growth.  Here's a link on forteo from the Cleveland Clinic if you haven't read it already.

You'll have to decide for yourself what to do for treatment, and do as much reading as you can, but from reliable sources.  I would hope you could find benefits for osteoporosis with just exercise and supplements, but generally this alone is not enough.  Once you stop producing estrogen you loose bone mass at an excellerated rate, so you have to compensate for this with something that either slows bone loss (bisphosphonates=fosamax, actonel, boniva etc) or with a drug that stimulates new bone growth (forteo). 

Here's a link from the New England Jour of Med on "More on Atypical Fractures of the Femoral Diaphysis. (July 2008)"  See pages: 316-318 for more explanation on this topic of rare bone frax's/brittle bone, and secondary factors that contribute to these problems.

Good luck finding something that will work for you!!