I had osteoporosis by the time I was 44. 5'7" at the time and lean. I asked to be checked because I broke 6 ribs.
Fosamax heled me a lot, but I can no longer take it because I was on it for 15 yrs!
You need to carry extra weight, but it doesn't have to be your own body weight. Walk with a backpack with water in it. Maybe the camel kind, so you can drink as you walk. The water will be inside you instead of on your back, but the weight won't be gone until lots of sweat and pee.
The bones can recover some (back to osteopenia at least) with the calcium, vit D, and weighted exercise. An activity tracker helps me. They can remind you to not sit, or give you points for moving and take them away for excess sedentary time. I also have a vibration platform, but no particular way to see benefit of that independently of other changes.
FYI, I have always had very small bones for my height, and have family history of calcium not getting onto the bones very effectively.
Just had a bone scan and my bones are great for a 51 year old and I am slightly overweight and in menopause, but my mother and grandmother have/had great bones. The extra weight is like weight bearing for those bones. I do strength training mixed with aerobic exercise. I say get out and walk more (brisk) and avoid excessively sitting. Too much sitting is terrible for someone with back issues. Yes, I know all about that. You want to sit when you have pain, but that actually only makes the situation worse. Has to be a balance between sitting and moving. What's your weight lifting regimen like? Free weights or Nautilus equipment? Again, increase your walking. As far as your medications you definitely should follow the advise of your physician. And no, you aren't too young to have osteoporosis. My sister-law-in has it and she is underweight and doesn't do much sport or activity. Weight lifting and nothing else isn't going to do much. You're vegan too, which means your calcium intake isn't the best. I don't really believe in extreme ways of eating unless your physician recommends that. Vegan is too extreme for an older woman in my opinion, but that's for you to discuss with your physician.
Do you know that I had the bone scan done in my early 30's and was told I had the start of osteoporosis? But I was VERY skinny, work out queen then and they said that was common if you fit in to that category. Are you very thin? Just asking. But in general, as we lose estrogen during menopause, osteoporosis is more likely to develop. Here's a fact sheet on it. https://www.niams.nih.gov/Health_Info/Bone/Osteoporosis/osteoporosis_ff.asp Just one more pain in the butt thing to think about as we get older. Grrr.