So sorry you have this worry, it's horrible, I swear it can make you feel like you're losing your mind.
I just went through this at the end of November, had bleeding/spotting for 7 weeks. But my dr did everything all at once, pap, endo biopsy, bloodwork, ultrasound. Seems they need all those things together to make a diagnosis, if you leave one out? It causes this kind of thing.
I do not believe the scan can tell them anything for sure, other then further testing is needed.
My thought is that you're on your way to an endometrial biopsy. (just the word freaked me out). My dr did it on the first visit, right after my pap. I was also kind of scared because she said .. "I can do it right now". Ugh !
So if your dr says that, just do it, get it over with. My experience was not bad, my dr had the nurse come in to hold me hand if I needed it, but really, it was little discomfort and over pretty quick. I did bleed a lot from it, and it was for a week.
In the end, I have fibroids. All the while, I was positive it was much much worse then that.
Chin up !