Inability to co-ordinate

Hello all
I'm fortunate to be able to live a fairly 'normal' life with my ME/CFS; I work for myself so can dictate my hours, am able to rest up, and able to travel, walk, drive, though they all have payback and require rest, plenty of planning and making sure I don't do too much. Every now and again my symptoms flair up unusually just to remind me not to be too sure I'm doing ok lol....
Yesterday evening I was able to visit our local church for the candlelight Christmas carol service, where our daughter was singing and doing a reading. It's a 3 minute walk from our house, but we drove it as it's cold (I know, lazy lazy).

The church was full - probably 150 people - so the environment was noisy (which is normally a trigger anyway). At the start all the lights are turned off and the Vicar will talk under the light of a single candle. So far, so good.
We are all given a candle to hold, and when these are all lit we start the service. There's a choir singing, pipe organ and a small orchestra. I'm doing ok with all of this until it comes to the congregation having to sing the first carol.

I'm holding a lit candle, a paper order of service with the song words printed on. I'm concentrating on holding the candle steady enough to not set myself on fire (or the person sitting in front), while trying to read the words to the carol, compute what the words are, try and sing the words, while standing still....and not set fire to anyone.....

The problem was: I froze. As I tried to make out the words on the sheet my brain seemed to stop. I couldn't physically speak or sing, and my legs started to buckle underneath me. I tried and tried to do all four things at the same time and it was as if my body said 'no'. Now this is a new one for me because I was in a similar situation a few weeks ago and had no problems at all, so I'm not sure what was going on. My wife said to blow the candle out, which I did, and after 20 minutes it was if my brain had started to relax and I could now at least read the words and understand what they said, and eventually I could sing a few of the last carols. I came home feeling exhausted, and today I have a hangover feeling from it all, very achy, and my legs are in a lot of pain.

Has anyone had a similar experience to this? I'm experiencing some issues with arm and leg muscle weakness, and a tremor in both arms at the moment which my GP is referring me to the neurologist soon, but other than that my symptoms tend to be the normal PEM/muscle pain/exhaustion/headaches/sinus pain issues a lot of people get.