If you don't wear your retainer for a while and your teeth get crooked, would wearing them straighten them out?

Lost ground. If movement minor, and you can get retainers to seat, you may be able to recover a portion of what has been lost, but not all. Wearing retainers intermittently can actually destabilize teeth. They must be worn as directed. If retainers don't fit, may require retreatment. In either case you owe it to yourself to call your orthodontist immediately and come clean.