Something to remembers is... any lump, sore or spot that has been in your mouth for more than 2 or 3 weeks that does not automatically resolve itself on its own, needs to be checked by a professional.

You will need to be your own advocate. The toothaches is probably unrelated to the spot, but only a professional can tell you that after an exam. You know your body best and know when somethings not right. I suggest to think about this long and hard then decide either to get it checked or take the 4 ENTs advice. If you have not felt you were listened to after seeing 4 ENTs, could it be possible that the 4 ENT's are correct and its nothing serious? If you feel it needs further checking then find someone to do the biopsy and you will find out what the spot is. The only way to tell for certain what something is would be to have it biopsied. I do not know how your medical system works in your country but here in the US, ENTs do specialize in oral cancer and preform biopsies. You nay need an oral surgeon or dentist? In the US biopsies can be done by any of these professionals.

Hopefully you do not have cancer. Best wishes!