Welcome to NT Robin...sorry you have the qualifications to join our club...

I also was diagnosed late-53. My main symptom is spasticity and pain. You describe my experience the day after a workout.
I have learned to try to stretch every day-there's a pamphlet on the natl MS society site showing effective stretches. I also take medication to lessen the spasms.
It's difficult to know how hard to push yourself, especially if you're trying to get in shape or lose weight.
If you are experiencing this much discomfort, my recommendation is to do some VERY gentle stretches and rest your body. The spasticity will cause fatigue and a feeling that you have molasses in your veins. I know that standing in line for more than a couple of minutes brings on instant spasms and pain for me, so I get what you're talking about.
I'd also let your neuro know if this keeps up-you might need some muscle
relaxants.
Keep us informed of how you're doing