If this your first yeast infection, I'm assuming it is since you're asking, you need to see the dr. They may just prescribe diflucan or an otc product but they usually want to see you the first time just to make sure that's what it is. Since you're on antibiotics I'm pretty sure it's yeast.
When you take antibiotics for a certain period of time, they can cause you to get a yeast infection, which can lead to the itching you are experiencing. My advice is to contact the doctor or whoever prescribed you the antibiotic and let them know, they can tell you the best thing to do from there. Also, drinking lots of water and eating yogurt with live and active cultures might be a halp, if this is in fact a yeast infection you have. I hope this was some help! (: