While it is unfortunate you had five repeats, no real harm was done to you. There is no level zero of risk from ionizing radiation.But as you know we are all of us exposed to natural radiation, and the level of radiation from diagnostic imaging is comparably minimal. The damage can be repaired by the cell. You have received an effective dose of 0.05 mSv ( millisievert).
This is lower than from a CT of the brain which gives about 0.09. It is even higher with the modern multidetector CT.
The panoramic is done with a thin beam, which means that the radiation is confined to the area of the mandibles which does not contain critical organs.The quantity received by the lens of the eye is negligible.
The maximum allowed yearly dose to the
lens for members of the public is 15 mSv.
For the radiation workers, it is 150 mSv.
So you are on the safe side.