Endometrial misery

Hi guys. I’m gonna cut a long story short. 
I had an endometrial biopsy after post meno bleeding. I was diagnosed with adenomyosis, multiple cysts and slightly thickened endo from a US scan. I’ve had to chase for the biopsy results today. Anyway, they said the sample was insufficient/inconclusive and I now have to go back next week for a hystereoscopy and further biopsy. But why didn’t they just do that in the first place?! I am so stressed. The biopsy was incredibly painful & traumatic and I’m panicking at the thought of having it all again. 
Anyway, why would a biopsy by inconclusive. Either there’s cancer cells or there’s not. 
I had an abnormal smear which was kinda the start of all this. My colposcopy showed nothing concerning. Just odd this has all followed on from that. Scared. Anxious. Not coping well