While green, clumpy, or any kind of abnormal discharge from your vagina may be a sign of STDs, it can also be a sign of other infections. One common possibility is a yeast infection, which can cause this type of discharge. It could also be a sign of another bacterial infection. Or, you may have an STD and not be aware of it.
If you have abnormal discharge, such as it being green, thick, clumpy, or having a bad odor, go to see a doctor immediately! They can test and see what the infection is, and give you medications to treat it. Once you are diagnosed by a doctor, treatment is typically just a few days of taking pills, and then you will be good to go!