Transvaginal Ultrasound Reasons

I am scheduled to have my second TVU in two days. The first one was a month ago and showed that my left ovary was significantly bigger than my right and I had free-fluid in my abdomen. My Doc scheduled another one to see if this is normal for me. What are the other reasons that I might have a large ovary and free-fluid? I'm nervous! My sister-in-law is on here so I'm posting anonymously as I don't want family to worry. I'm not pregnant either-that's why they did a TVU in the first place to see if there was a ectopic pregnancy.