ok... ive spent well over 30 hours on my map so far, and im haveing HUGE problems... its looking nice (according to me anyhow) but its EXTREMELY laggy. right now its just a church with a flag cap in it, and a small landing beach where there is a flag at the top of the hill. the walls of the map right now is just a sky texture (no i didnt make a skybox around the map... its only the walls)

anyone have any ideas how to fix this, cause i really wanna make it bigger....

http://collective.valve-erc.com/index.php?go=polygon_reduction_1
http://www.cryotank.net/maps/tutorials/rspeeds1.html
http://www.slackiller.com/tommy14/rspeeds.htm
http://collective.valve-erc.com/index.php?doc=1043477348-95410300

Good readings...
Also check the example maps from www.mardymouse.co.uk

You may have a leak or something in your map.

Quick check list
1) Examine .LOG file for errors and warnings
2) Is map full bright ? If yes, someting is wrong unless you have set such light settings
3) Enable r_speeds on the console and walk your map viewing at shown values.
If they are higher than wpoly 1000 epoly 10000 that's not good.
For more info look at links posted above.