Teeth keep moving until you're in your early to mid-20s because the jaw is still growing. Your best option is to get a new retainer made as soon as possible if your broken retainer can't be repaired. If you are unable to visit your orthodontist, you may be able to ask them to remake your retainer based on their records if you haven't had it for a very long. They can ship it to you or an orthodontist close to you can have it fitted. This will save you the cost of having the entire process redone.
Alternatively, a cheap removable retainer could help to support your mouth until you are able to get a new fixed retainer created.
If you've made the investment in orthodontic treatment to achieve a beautiful smile, don't let a broken retainer undo all that hard work. Get a dental opinion as soon as possible about whether your retainer needs replacing, and arrange a payment plan with your orthodontist that enables you to get the treatment you require.