kathy86, talk to your endocrinologist about starting a new medication before your Dec 6 injection is due. You likely know that you can't stop Prolia for a few months, You can't even be late for your injection without risk. I'm not so happy with Evenity, but in your situation I think be the may be the best bet. You'll need to look at the side effects of Evenity before deciding.
You probably already know this but Prolia works by preventing osteoclasts from fully developing. After a short period of time you build up a pool of undeveloped osteoclasts that are unleashed as soon as you stop the drug. The destruction of bone follows swiftly. You'll need protection.