Sally, I realize I'm a newbie here, but, this is my specialty. I've been an insomniac since the age of 11. I had a sleep pattern that I understood until this mystery disease started messing things up.
Sometimes, your body will go into "rogue" stage. It means that it needs to recharge. Especially after a stressful period, or if you change medications or change something as simple as how you deal with a particular symptom (i.e: change exercises or when you fall & recover).
Those Zen folks aren't kidding when they talk about everything having a place (feng shui) and a time for every season. And seasons also play a role in how your body reacts to things. Winter is coming...(not just a tag-line for a show like "Game of Thrones," LOL). Your body knows that it will react to less light, less warmth & needs to get your biorythym (sp?) ready for that.
Definitely, call your doctor to make sure it isn't something else; but, also, enjoy the extra sleep. A recharge isn't as bad as you might be worrying about it. All things in all good time. Simple but true.
PS: Scatter thoughts are brought to you by the good folks at: not sure what this is as an undiagnosed mess of a person