Hi hun. Let me first ease your mind by saying that you absolutely don't have ovarian cancer. However, as I was reading your story, I thought "Poor thing, she sounds just like me." I have endometriosis. My periods have always been weird. I would always get a period every month, but they were always between two and fourteen days late, and they were so very heavy. I don't cramp a lot from my period, but I get an unbearable pain in my pelvis after having sex if I'm about to get my period. You really ought to visit a specialist in this area to get a work up.
However, I'm not sure endometriosis would cause the vaginal symptoms you're having (although, I hate to say it, but I'm having those too! So who knows anymore? :P). It's entirely possible that you do have a bladder infection. How would you describe the pain in your vagina? Is it numb? Throbbing? Sharp? Does it hurt all the time or just when you wipe or come into contact with it? Any other symptoms of a possible infection, such as discharge, smell or itchiness?