I think you are probably right, but it could be many things that are causing you to feel unmotivated. Ruling out other things can be a helpful way to begin re-engaging.
I’d make an appointment with your GP and then pick one small goal to complete for yourself each day until you get your physical. The small goal could be cleaning a closet, reading a chapter of a book, helping your child with homework, or making dinner for the family. The goal isn’t as important as setting it. It needs to be simple and brief. Doing the small goals helps us with the larger ones.
Once you have the go-ahead from the physician and there are no physical issues responsible, you may want to consider some therapy to help with the motivation. The Find Help tab at the top of this page can help you find a therapist in your area, and our forums found here can get you connected to others who have found ways to cope with similar situations.