@cheesegrits, sorry to hear that you have not had positive results with your meds. Personally, I have doubts about the effectiveness of anti-resorptives to build strong bones but that's another discussion.
You should confirm with your doctor but I have read that once you have taken 4 or more shots of Prolia, Alendronate may not be potent enough to suppress any rebound effect and the usual recommendation is to use Reclast as the relay drug - with close monitoring of bone turnover markers esp CTX