wet spot???

Today, when i was just chilling around school and i felt like I was suddenly wet down there. It wasn't pee, I'm sure. I wasn't horny either.  It felt like a leak or something  When i got home, there was a whole wet spot that was about 2-3 inches big on my (new) underwear. There was no stains, but the substance was clear and very water-like. It later became to have a vinegar/sour smell. When i wiped my vagina, it had slimy yellow discharge. but what is this whole water-like liquid coming out with no notice??? This isn't the first time this happened btw. What is this? What's up with my lady part makin this smellly and uncomfortable substance?