Horrible yeast infection

Hey y’all I’m posting in hopes that someone can HELP me 😩. Ok so I’ve been on these super strong antibiotics that are prone to giving me a yeast infection and I was too sick at the doctor to remember to tell him that and I’m paying the price for it now. I did call back and he called me in a pill at the pharmacy and I went and got it and took it right away but I’m still DYING. I have never been so itchy and irritated in my life all the way from my clit to my ass and I don’t know what to do about it because it’s getting so red and sore/irritated from itching it but I can’t stop. How long do I have to be in agony before this shit kicks in? Should I go buy more over the counter too? PLZ HELP 😫