How Should Vaginal Itching And Irritation Be Treated?

I was diagnosed with strep throat on Wednesday of this week and given Penicillin VK 500 mg to take twice a day for 10 days. On Thursday night, I developed a severe vaginal irritation and itch and now it is worse. I am prone to getting yeast infections from antibiotic use so I used an over the counter yeast infection treatment Thursday and Friday night but it did not help at all and only caused burning. I noticed online that one of the side effects of Penicillin VK is vaginal itching and irritation. Does this mean a yeast infection? Or just irritation? What should I do to treat this? I do not have any white discharge like I have had with other yeast infections in the past. I have also used Vagisil to lessen the itch which seems to work for a while. Thank you.