What should I do regarding expiations for interrupting prayer after swearing not to interrupt it due to obsessive doubts about intention, and is one expiation sufficient for all?

If the oaths are made intentionally and by choice, then one expiation is due when breaking them, even if the oaths are repeated for the same action or for different actions before expiation, because they are expiations of the same kind, thus they intertwine. However, if the oaths are due to obsessive thoughts (waswasa) without intention or will, then nothing is incumbent upon you.