There is no harm in taking the test. I don't see why having a yeast infection would prevent you from getting your period or from getting pregnant. When you get the test, read the instructions carefully to see when after your missed period you should take the test.
Have you been treated for the yeast infection? This would be a good excuse to go to the doctor and ask for birth control pills (if you aren't pregnant, that is). I don't know where you're from, but if you live in the U.S., your doctor can't tell your parents about you asking for birth control without your permission.
However, I would suggest talking to one of your parents about this, or at least an adult you trust and ask them to take you to the doctor.
Good luck. Let us know how everything turns out.