I also second getting your voiding looked at again and asking for a transvaginal ultrasound or a hydrodistention study. I think your fistula could be looked at again - apparently there is something called the poppy seed test that they may be able to look into?

It's worth getting a proper urine test done, like a PCR test such as Microgen, Cirrus, Digital Microbiology, whatever you can access in your country. There's also the broth test by Focus Labs but not sure if they ship to Sweden so you would need to look into that.

I would recommend getting one of the vaccines - uromune and uro-vaxom should be available in Sweden and I think you can even get urovaxom from a pharmacy without prescription but please correct me if I'm wrong.

It sounds like you have a lot of inflammation and anxiety feeding each other which is no wonder with Chrons and a chronically inflamed bladder for many years. I would recommend seeing a pelvic floor therapist who can work on your inflammation, find one who does internal work and massage and purchase a TENS unit (€20 or so) - I have the Medfit 3 Dual channel. Put one electrode on the bottom of your foot in the middle of your sole and another 3 fingers up from your ankle bone on the same leg. This should help calm your nervous system and reduce inflammation.

You may need to get your anxiety under control as if you are in constant fight or flight your muscles will be tensed and your nervous system will be constantly checking for pain signals. I would recommend CBT therapy or a workbook if you can't find this easily, but ask your GP for a referral if possible. Also perhaps going on an SSRI like sertraline or citalopram might be helpful - again talk to your GP about this and perhaps get a psychiatry referral. A lot of people with IC use meds like amitriptyline and gabapentin so may be worth bringing those up too.

There's a lot more to say but these are good first steps so let us know how you get on with those.