My yeast infection returned after 1 wk. I'm afraid it's serious or it may be b/c current antibiotics for throat. See doctor or just use OTC medicine?

See your doc. If you are having chronic problems with yeast infections and/or get a yeast infection while taking antibiotics, you should be seen by your doctor so that it can be properly evaluated and treated.
Get help. Don't continue to guess and suffer the burning pain. Get the help of your physician. This can be figured out so easily.