I was first diagnosed with Osteopenia in my 20s in all three areas (femur, spine, hip), and then got it upped to Osteporosis in my spine a few years ago (I'm 43). I didn't start running until my mid-30s - a decade after I first was diagnosed with Osteopenia.
Post-osteoporosis DX, I managed to get my spine back down to Osteopenia with a) large doses of vitamin D (4000 IUD a day) and b) being really careful about avoiding gluten and lactose (I'm intolerant of both, and when I consume either my GI tract gets inflamed and I don't absorb the nutrients I need - I'm pretty sure this does not apply to you)
I would strongly suggest getting your vitamin D checked, and talking with your doctor about supplementation. (note: I am NOT recommending that you just start supplementing without discussing with a medical pro first).
I'd be very wary of Boniva, Fossamax, and similar drugs. My understanding is that they work by slowing bone turnover. Which is great for little old ladies who are shedding bone mass and not replacing it - it slows their bone loss. However, younger people like you and I are constantly replacing older bone with new bone, as a response to the stress we place on our bones. And that's a good thing. And I'm very fearful about interfering with that process.
There's not the same depth of literature and studies for use of the bone density meds in younger women as there is in post-menopausal women. And that worries me, because pre-menopausal and post-menopausal are two completely different populations for purposes of this discussion.
I'm also not sure that bone density is the best metric of bone health. Bones can be dense, but brittle.
FWIW (and at the risk of jinxing myself), I have had two broken bones in my life - one was a broken wrist from a fall as a kid; the other was a broken 2nd metatarsal - it snapped while running (I made the mistake trying to train through a posterior tib injury on my other foot - this was a compensation injury). Interestingly - the bone density in my feet is supposedly excellent.
I've trained for and run 7 marathons over the past 5 years. In the past few years, I've generally hovered around 55-60 MPW when training; in the past I've run weeks of 80+ MPW, even up to 90+. I've yet to have any fractures in the areas noted as trouble spots on my dexa scan. (Again, fingers crossed). My injuries (excepting the one broken metatarsal) have always been soft tissue - plantar fascititis, high hamstring tendonitis, etc.
I hope this information is of some help to you.