In the last 5 months I have had canker sores once or twice a month. It started before I moved and on an orange juice guzzling week (thinking it was stress and acidity) and then from then on it's been once a month, sometimes twice, in many different places. Sometimes under my tongue or on my gums or inside the lip. They're pretty painful and last for almost a week. Is there anything I can be prescribed to make this happen less often considering it's borderline chronic?
First, it is a good idea to have these lesions evaluated when they are present so we can confirm they are aphthous ulcers (canker sores) based on the appearance. They do sound like it but there are some other inflammatory conditions that can appear in the mouth. When they are this recurrent the first thing we recommend is to stop your current toothpaste and use only a paste that is for sensitive gums --Rembrandt brand has one and there are now some others that are being marketed.
It is true that canker sores tend to happen more with stress but doing some basic blood work would reassure us that you don't have more issues causing them. There is a prescription steroid paste that can be helpful in healing them a little faster but there is no "preventive" other than trying to determine the cause and avoiding exposure to it as much as possible.