Finally i managed to fix it!
First thanks to all u helped me.
Now the fix is very simple.
I moved the initialization of the String month to inside of onCreate method with no value. i also extended the if statement to assign the value true if was the firs time running or not pressing any button.
String month = "";
Bundle extras = getIntent().getExtras();
if (extras != null) {
month = extras.getString(month);
}
else{
month = "true";
}
I also initialized with no values the month variable in the onClick methods
String month = "";
very simple but it took me 2 days to figure out! ;p thanks again guys