I got back to normal after about a month of supplements and sunlight. It happened to me again a couple of years later to a much lesser degree since I had just forgotten about supplements and then once again was resolved the same way.
Don’t confuse correlation and causation. Maybe you were going to get better anyway and it just coincided with the supplements. Maybe the second time was something completely different.
I did X and now I feel better is completely meaningless without some quantitative supporting evidence providing a link between the two.
There’s a reason why the double blind trial is the gold standard of medical proof.
You may of course have this evidence, I’m just commenting on what’s written in this comment.
A billion people are vitamin D deficiency. Many are asymptomatic.
Did you have a viral illness causing your symptoms and it got better? Was it the vitamin D? It is hard to say. Some supporting evidence would be you had a previously normal vitamin D level back at your old GP.