Is this hypermetabolism?

So for a while now I was getting around >!10-15k!< steps a day and eating I’d say like >!1100-1400!< at most a day. I have been dealing with some health issues so I got a work from home job and have stopped walking and getting steps in. I probably at most get in >!3-5k!< a day and eating >!1400-1600!< a day currently. My weight has been at a plateau for I’d say almost a year. It just now as I’ve been eating more and moving less, it just keeps going down. I don’t understand at all I thought I’d be going up considering no movement.