PAIN IN MOLAR REGION. Reason for this?

Although the OPG is not very clear, it shows that your lower left wisdom tooth is not in proper angulation and is impinging upon the second molar. Based on the description that you have mentioned and the photograph that you have attached and without a proper clinical examination, the only rational opinion that we can provide at this point is that the pain could be either due to inflammation of the gums around the tilted wisdom tooth or or or the pressure affect it is causing on the second molar. And because such tilted teeth are usually not properly functional and because you are having this problem for a very long time it would be prudent to go for the extraction of those tooth for permanent relief. It might seem like a drastic step to you at this point but please understand that this tooth is not going to change its position and the risk of damage to the second molar always stands. And I hope you can make out a triangular shaped area between the second and third molar which is going to be prone to gum inflammation on a regular basis and will not be amenable for proper tooth brushing. Regards.