i.. Welcome to Healthcare Magic. I have gone through your query and can understand your health concerns.. As per your complain sores on roof of mouth can be; 1. Apthous ulcers or canker sores.. 2. Cold sores caused by Herpes virus. 3. Allergic reaction to medication. 4. Bullous Pemphegoid.. You should consult a dentist and get evaluated and in case of apthous ulcers you should do warm saline gargles. Gargle with 1:1 solution of hydrogen peroxide and water.. Apply milk of magnesia over the sores. Take a multivitamin tablet for 15 days.. In case of viral infection antiviral oral and topical application like Acyclovir therapy can help in preventing further outbreaks.. In case if it is due to allergic reaction anti allergics like Levocetrizine or Benadryl can be advised.. Salt water gargles will help. Avoiding the allergic food can help.. The white patches over the palate and as you already told that you have yeast infection the patches are due to Thrush.. For this you have to take antifungal medicines like nystatin mouthwashes will help.. Suck Clotrimazole lozenges.. Take more of probiotics like curd and garlic can help.. Hope this information helps.. Thanks and regards.. Dr.Honey Nandwani Arora..