We also have a fixed female cat Lexi who was from a shelter and had already had a litter. She is a cat who goes in and out all day as we have a cat door.
We have a shed in the yard, a woodchuck was living there but now Lexi frequents the spot under the shed.
Last week we had a bad snow storm and the entrance was covered. She was very upset until I dig out the hole so she could check in there. I often think she is looking for her kittens. Maybe your cat also has had a litter.
