What is the best way treat a severe yeast infection? when should i be worried?

"Azole" drug: There are many treatments, including over the counter ones, mostly with active ingredient ending in "azole" (clotrimazole, miconazole, fluconazole, etc). However, severe cases need check for problems that predispose to yeast, especially diabetes. See a doctor to confirm the diagnosis and get proper treatment. If you try OTC treatment, for sure see doctor if not better in 3-4 days. Good luck!