Yep, Cath is right on.
There are plenty of us who have gone through the same stuff.
This will help you...when you do anything to challenge yourself....examples: go into a busy place, go shopping, do new or harder vrts, walk, run, bike...whatever....it will cause a delay in worse symptoms.
What I mean is say on Saturday/Sunday..I am really busy....Tuesday/Wednesday I tend to be off...
Now that I am better I am off less, and less severe. Initially though...it would be really off...could be for a few days.
Hope this helps.