Help with Spawn Trigger

I am having a very hard time getting my spawn trigger to work right on my tower defense map.

It works sometimes, but on some level it doubles. For instance,

once level 3 is complete it spawns level 4 and level 5 at the same time. and then on another level, before that level is done it spawn the next 3 levels! I based this trigger off of another maps' trigger, and made the correct adjustments in the varibles and unit editor.

I am using 2 intergers and a unit group varible

" i " is my counting varible
" level " is my varible to keep track and display what level it is, this varible actually has nothing to do with what spawn, just what the message before the spawn says is going to spawn.
" attacker " is my unit group

basically after the first 30 seconds of games time my spawn trigger starts to run. the spawn trigger works like this.

E
every 2 seconds of game time
C
player 12 food used = 0
A
Create 12 Attacker(level) blah blah at SpawnPoint1 facing triggering unit.

I have another trigger running from map start that look kinda like this
set i = 1
set attack(i+1) = footman
set i + 1

and it goes down from there, I am at work now so this is not exactly right, if anyone wants to take a look at my map i can email it to them, or if you know a simple way to solve my problem let me know.

Thanks alot.

look at this map, it has everything explained in it...