Hi
I don't know if it's a bit late to reply to you but in case others, like you, are reading this post.
It's very, very unlikely that you have vaginal cancer. Vaginal cancer is extremely rare anyway and when it does occur it is usually in women over 50. My grandmother died of it and I researched it a bit when I myself developed cancer of a different kind so I know a bit about it.
Having said that, of course, you need to get yourself checked out and find out what is causing your problems. I expect you have already done so.
Don't assume it's cancer. Women have bodies that are very complicated. It may be a cyst of sort and there are numerous non cancer, benign afflictions we get. Stay positive and make a list of questions you want to ask the dr so you won't forget in the event you get nervous.
Try not to worry!
I'm a guy, and old guy, so I am off to a bad start at having any direct experience... but my wife, an elderly woman has had ovarian and uterus cancer (is the latter what you are concerned about?). She had the problem areas removed with surgery and chemo follow up.
Hum, why to I reply? I just want to say it is unlikely you have cancer and it is good you have an appropriate medical appointment. My advice is to believe you do not have a serious problem and that your doctor will know exactly what needs to be done, if anything.
You have my (our - others who read but have no experience to share) best wishes and believe you will be okay, all will turn out well.