confused with symptoms and results

I am a 23 year old female with a family history of breast/ovarian cancer.  A few months ago I noticed unusual bleeding in between periods wthat has since become heavier,(particularly lower left) pelvic pain, bloating, abnormal bowels and general fatigue.  I saw my family practictioner who ordered a CT scan. The nurse called with the results and said there was an abnormality in the uterine area and refered me to a gynocologist.  After a painful pelvic exam she ordered a pelvic ultrasound.  During this, the sonogramographer had difficultly locating the left ovary and was confused by a "light spot", after a few different technicians examined everything they concluded that the spot was a result of my tampon and that my uterus appeared normal.  This was about a month ago and my symptoms have continually worsened--my question is whether pelvic ultrasounds are sufficient in detecting ovarian cancer, could the tampon have masked a problem? Thanks so much.