Thanks for putting up your question on Just Answer.
So as I understand , a dentist and an Endodontist have both given you a clean bill of health for the front tooth in question.
Do you have access to the latest X rays of that tooth? Can you upload them here?
For the moment, let us assume that they are right, and the tooth is normal. Then there must be another explanation for your pain.
There is a grey area of orofacial pain , what we term as Atypical Facial Pain or Atypical Odontalgia, which does not respond to any therapy, and for which no cause can be found.There is nothing wrong with the teeth or gums. This type of pain is common at your age and gender. It can be provoked by dental treatment, underlying systemic disease or it may be brought on by stressful life events.
These different types of pain do no not respond to conventional treatment, like antibiotics and steroids. They require non conventional treatment like sedatives, anxiolytics, antidepressants, physical self regulation, cognitive behavior therapy etc.
I suggest you visit the Orofacial Pain/Oral Medicine department of the dental school nearest to you. A full assessment is required to eliminate any underlying cause. Screening tests should be carried out to exclude hematinic (blood) deficiencies and to rule out diabetes. If all this is negative, there might be an underlying psychogenic cause(anxiety).
I also urge you to try alternative pain relief methods like acupuncture and Cognitive Behaviour Therapy- includes relaxation and breathing techniques and positive re-enforcement of thought.
Hope this answers your question. Feel free to contact me again for more information. Please leave a positive rating for me if this answer has helped you. I do not get credit for it otherwise.
Good Luck !