Hi, ! First off, I am sorry you are experiencing this change and I do hope it's temporary. I don't know what type of MS you have, but I do hope this new change takes a hike very soon.
Also, at the risk of being rude, I am starting the journey of "is this a new symptom to worry about or is this just aging?" Believe me, I am not enjoying this guessing game.
Odds are, in your case, that your MS is the culprit, but if you haven't done so already, I would definitely visit your physician and make sure nothing else is causing the fatigue and weakness. It can be easy to chalk everything up to MS, but it's good to doublecheck, just to be safe and thorough. And, your doctor may have some suggestions for changing your treatment protocol or even trying physical therapy. He/she will have the best suggestions for you.
That said, I wanted to share this article with you on the specific topic of leg weakness, as I thought you might find it helpful -- https://multiplesclerosis.net/living-with-ms/leg-weakness.
Again, I sure hope this new wrinkle in your life is fleeting and you start feeling stronger again very soon!
Best, Erin, MultipleSclerosis.net Team Member.