I believe i have a bad yeast infection, but there are blisters/sores on the inside of my labia minora. i can't have herpes. what else could it be?

Sounds like herpes: Yeast may be possible, but herpes is the most common cause of such symptoms. Why do you think you can't have it? Even if monogamous with a faithful partner, herpes is the best bet. Many cases of herpes show up in that situation; your partner could have it, without symptoms. Most important that you see a doctor ASAP, the earlier the better accurate diagnosis and effective treatment. Good luck!