Blood in urine, young female: Testing not showing cause

Has anyone had blood in urine (Hematuria) that doctor could not find what’s wrong. I’ve had urine test (negative of infection), ultrasound of bladder and kidneys (normal), camera up urethra and bladder (normal), blood tests all normal including liver and kidney function) and still no ideas as to what’s causing the bleeding. Just wanting to know if anyone has had something similar before. I’m female in my 30s and healthy person. It’s been two weeks with blood in urine which changes from pink to sometimes brown.
Any help appreciated! TIA