I Am A 20 Year Old Female. I Have Spotting

I am a 20 year old female. I have spotting almost throughout the month. I consulted a gynaecologist recently and she asked me to get an ultrasound done. The reports of the ultrasound said that i have 'thick and heterogeneous endometrial cavity along with fluid in it'. Now the gynaecologist is saying that i will have to get an abortion done because my case looks similer to someone who has had a miscarriage. Now what i am failing to understand is how could i have had a miscarriage when i didn't conceive at the first place because i have never, in 20 years of my life, have had a sexual relationship of any sort with anyone. Can someone please explain and tell me what else could be the reason responsible for my condition.