Can't access my own ftp? n00b question

i used to have a ftp server running, but that's back then when i didn't have a router.

i've set a new ftp server, tried 3 different servers (g6, serf-u and bulletproof), in all 3 cases, when i try to connect using port 21 it connects and says 421 incorrect login (even if i set the username to anonymous)
then i tried using a different port (above 10000) every port i've tried - it didn't even manage to connect.. it says connection refused right away.
i tried to set the server to passive mode, giving it my external ip (also in the client of course)
and ofcourse i have DMZ set in my router to my internal ip.
i only have windows firewall and it has permission (but yes, i tried to disable it, didn't help either)
when i active the server it says FTP Server On-line : IP(s) 192.168.0.5, on port 13000
no sign of the external ip (if there should be one)

oh and when i write my write my internal ip it connects without a problem. the problem only accures when i write my external ip. so therefor i sense it's a router issue.

and i've searched the web for hours.. every single site just says to forward the ports. but i'm on DMZ (but once again i tried forwarding the ports manually, didn't work)

currently i'm using BulletProof FTP server 2.21, and FlashFXP as a client.

anyway i need some advice, cuz i have none left
anybody can shed some light on this one?

Can you get to your server from outside your network not just from inside using your external ip?

nope
that's the problem.
seems like it can't figure out where to go once i put the public ip address.
thing is - i did manage to play games online
so it's not like there's something blocking me from the outside
first time i have connections issues like this.