I see you are in the Crohn's forum mostly so you might not know about Fibro 101...the first thread on the forum. There are links to good information about fibro and you will learn a lot there.
I also have Crohn's disease and you can get something they call Crohn's arthritis and maybe that is going on. Be sure to talk to your gastroenterologist about your joint pain.
I use malic acid/magnesium supplements and extra vitamin D3 and these have helped me with pain and fatigue. There are links about these in Fibro 101 and how they work in the body. Many with fibro are deficient in these vitamins and nutrients.
You, though, might have even more problems because of the Crohn's disease. I know I do because I don't absorb nutrients like a person without Crohn's. Consequently, I was very low in sevral nutrients including vitamin D. I live in Florida and we have a lot of sun but, whenever I'm out in the sun, I put on suntan lotion and that blocks the vitamin D, too. I see you live in Iceland. I'm not sure how much sun you get but you might ask your doctor about checking your vitamin D levels. They do this with a blood test. I take 5,500 IU of vitamin D3 a day now! It has helped with pain, too. It's a very important vitamin. You need vitamin D to help absorb calcium, too, and I was so low, I wasn't absorbing the calcium I was taking and ended up with osteoporisis because of it. So be sure to ask your doctor, okay?
These vitamins and nutrients, along with the exercise, have helped keep my pain under control.
Sherrine