What should I do if I vowed to do something and doubted whether the vow was for a single instance or for every time, then it became clear that it was for every time?

If the intention of the one making the vow was not to repeat the vow, or if the wording of the vow did not necessitate repetition, or if there is doubt about the intention of repetition; then he is only obligated once, because the default is the exoneration of responsibility. However, if the wording of the vow necessitates repetition, then he must repeat it whenever the condition upon which it was made is repeated.