After 15 years you are doing fine. Keep reassuring yourself because worry is needless and the continual anxiety can worsen (or seem to worsen) the onset of symptoms. You might want to spend a few days of self-pampering to allow your body some rest and recovery. You might also try to use some cold compresses on your legs.
For me, general leg weakness is something that I have just gotten use to having. Only when I have nerve pain do I aggressively go after it with a heating pad. Otherwise, I just keep my stretching and continue to use my passive Exercycle.
By the time you get an appointment, your current problem may have gone away. If this is you first noticeable problem in 15 years, you should get checked because MS can definitely change gears on you.
Welcome and I hope we can be here for you!