Hi Wentee,
Although I cannot provide a diagnose online I can provide guidance. Leukoplakia is a clinical term used to describe a white patch in the mourh that does not rub off and does not have a specific diagnosis. This is a clinical diagnosis only not a microscopic diagnosis. Without a biopsy you do not have a definitive diagnosis. The issue then becomes how to treat a lesion without actually knowing what it is.
The lesion is painful and long standing and obviously causing you both physical and psychological distress. I understand that you have had conflicting advice from multiple sources and I know that a biopsy can be scary however I strongly suggest that you have a biopsy and that the tissue should be sent to an oral pathologist for an accurate diagnosis.
On the positive side the leukoplakia has not changed in size, texture or color, and these are all good signs and suggest that the lesion is benign! The other benefit to having a biopsy - besides peace of mind - is that the process of having the biopsy done can actually help heal the affected lesion, the process of removing the lesion gets rid of dead tissue and brings fresh blood flow to the area which also supports and improves healing.
I suggest that you see your dentist who can smooth down any rough edges on your teeth. Orthodontic wax can temporarily be used to fill in the spaces between the teeth. If at all possible you should try not to play with the affected area as chronic irritation also can lead to swelling and pain.
If the leukoplakia has been present for more than six weeks it is not likely to resolve on its own and it should be biopsied. You need a definitive diagnosis so you can receive appropriate treatment.
I hope this helps,
Dr. Gwen Cohen Brown