What should I do concerning my repeated oaths (more than 300 times) to perform the prayer of thanksgiving, when I now know that it has no basis in religion, and that the expiation for these oaths would be difficult for me?

The oath of a minor does not necessitate an expiation, nor is his oath binding. If there is doubt whether he was a responsible adult at the time of the oath, then nothing is required of him. However, if a responsible adult swore to perform a prayer of gratitude upon receiving multiple blessings, then these are multiple oaths, and each one requires an expiation. The expiation for an oath is feeding ten poor persons, or clothing them, or freeing a slave. If one is unable to do so, he must fast three days for each expiation.