using a while and not a for

// untested
// set variables to known values
int findFirst = 0;
int j = 0;
   while(j < EEPROM.length()) {
      // check if your value is there
      switch (EEPROM.read(j)) {
        case acitivity1:
        case acitivity2:
        case acitivity3:
        case acitivity4:
        case acitivity5:
        case acitivity6:
        case acitivity7:
        case acitivity8:
        case acitivity9:
            found = j;
            findFirst++;
        break;

        default:
            // nothing matched
      } // switch closing
    if (findFirst != 0)
       break; // found it
    j++ //increment EEPROM counter
} // close while loop