Fatigue is very common in Crohns, as many of the previous posters have said. There are a variety of reasons and it depends on where you are in your recovery/remission process. There are plenty of other issues: poor nutrition, malabsorbtion, blood loss (miniscule but can lead to anemia), etc.
My first recommendation is to ask your doctor for a full blood panel to look for all of the above possibilities, such as iron deficiency, low B12, thyroid issues, even Celiac disease is a possibility. Anything can cause problems with your energy level, even depression or just having to go to the bathroom 7 to 20 times a day!
It is definitely worth talking to your doctor about
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My second piece of advice is -- be kind to yourself, rest as much as possible and try to get as much sleep as you can. In my case, a 20 minute power nap in the afternoon does wonders. I used to take lunch at my desk, close the door, lay my head on the desk and take 20 minutes then. The desk was uncomfortable enough that I never overslept (but you could always set an alarm - lol!)
Best wishes,
Sudsmom