Detection of a small amount of clear fluid is normal. Copious clear fluid may suggest a ruptured fluid filled cyst or ascites. Nonclotting blood would indicate active intraperitoneal bleeding. Pus indicates an infectious process, possibly as abscess.
Since you had a cyst and now it is gone(if transvaginal sonogram was read the 2nd time correctly) the fluid may be from the previous cyst which ruptured. As long as you dont have pelvic/back pain which could indicate further fluid build up I would not worry too much. As always ask your GYN what he or she thinks is going on and what if any further tests/blood work may be needed.
The best advice you see all over these posts is you have to be your own advocate, be aggresive and stay on top of your phycicians. Get copies of all your tests/results as you are entitled to them. Post with any other questions you have this site has some very knowledgeable people on it. I wish you all the best.