Why do i keep getting a heap of mouth ulcers at once every few weeks ?

Needs evaluation: I recommend that you see your dentist for a complete and thorough medical and dental history, along with a clinical examination and x-rays. Then your dentist will be in a better position to answer your question. This is not something that we can accurately diagnose over the internet.

Need to see a Dr: I agree. A proper eval is needed to identify the cause and possible treatment for multiple sores. It could be a number of things from apthous ulcers, to viral, or fungal cause. If it keeps re-occuring you can discuss with your dr to identify if perhaps there is a specific insult causing the flare up, such as spices or cinnamon. But again, it all depends on the actual cause. Best of luck!