First: get a full “senior” bloodwork panel done. Rule out anything medical.
Second: hide all trash and all food. Counter and garbage surfing are self-reinforcing. Lock the trash away, get a locking can. Remove all food from all counters and put them in a secure cabinet. Lock the fridge with a child lock, if necessary.
Third: Crate when you can’t supervise.
This is usually medical if it’s sudden like this, but you need to be proactive in your prevention, and it’s always a multiprong approach.
Hello,
I think that the best step you can take is to see a vet and talk to them about your concerns and suspicions. Ask for help in addressing pain and anxiety. I like gabapentin for cats but there are lots of other options to discuss.