Had lots of sex two days ago, long term relationship, yesterday had yellowish clumpy discharge and today it's brownish, very sore vagina too?

Discharge: A yeast infection or bacterial vaginosis infection can cause your symptoms. So can a sexually transmitted infection. A yeast infection can be treated w/ otc meds. Treatment for BV needs a prescription. The best way to know what it is is with a good exam and looking at a sample of discharge under a microscope, along with std testing.