Nagios notification intervals


I have my Nagios machine configured to send out notifications, however for some reason it seems as though if a host goes down, I sometimes don’t get a notification at all, and if they do come through its a notification saying it is back up. What would be a reason for these delayed notifications? Is there something that I’ve missed? Here is a portion of my configs:

notification_options d,u,r
notification_interval 120
max_check_attempts 10
retain_nonstatus_information 0

max_check_attempts 5
normal_check_interval 5
retry_check_interval 1
notification_interval 30
notification_options w,c,r


What did you put in for the conacts notification options? Mine look like this.
define contact{
contact_name justinm
alias Justin
host_notification_period 24x7
service_notification_period 24x7
host_notification_options d,u,r
service_notification_options w,u,c,r
host_notification_commands host-notify-by-email
service_notification_commands notify-by-email
email justinm@blah.