It does sound like you've got a tunnel between the bowel and vagina, and since you've never had evidence of such a thing before, like it has only recently appeared. (Which is not uncommon. It would be more unusual to have had one since birth. They can sometimes form in just a few days.)
Yes it's a serious thing to take care of, and of course it's also a hassle for you. I'm glad you will see the ob/gyn in 2 days. In the meantime, can you wear "Depends" or other incontinence underpants? It will save on general hygiene while you wait for your doctors to help you.
Here's from another website about the general topic of vaginal fistulas: https://my.clevelandclinic.org/health/diseases/22260-rectovaginal-fistula
If you think you will be too anxious to have the exam, call the gyn's office and explain this, tell them it's serious enough that you couldn't have a pelvic exam before. Ask if the doctor can prescribe you one Valium, to take an hour before your appointment. That will help. You won't be sleepy, but will be less anxious.
Pelvic exams are uncomfortable but not painful. And if the doctor needs to look into your vagina, a pelvic is how it's done. Vaginas are naturally closed, like a mouth, (though obviously they can stretch enough to let a baby out). The speculum is similar to if a doctor who wanted to look in your mouth were to use some plastic salad tongs, slide them into your mouth, closed, and then open them once they're in your mouth to look at your teeth. You do need the doc to see what is going on in your vagina. Sometimes it also helps if you can have the doctor narrate what she is doing as she goes along.
If worst comes to worst, you can be knocked out for the exam. I'd try to not let it come to that, but it is an option if you can't stop panicking.
Obviously, stool has no place in a vagina. Talk to the doctor about maybe getting onto antibiotics in the interim while they decide what to do to mend it.
Good luck! Write back and tell how it went.