So basically i modified breezehome, added rooms tons of deco's and ect . .
But when i added the last room the game crashes each time i exit the house, if i use the console "COC Whiterun" i teleport outside fine, the problem occurs only when leaving through the door, and entering works fine, i have generated a navmesh and worked it around abit but to no avail, i have searched for an answer around two days now, please help !
Does the problem occur because of the nav mesh ?

That's a common bug when the interior that is linked to a worldspace other than Tamriel is "too big". So if you're new Breezehome is significantly larger than the vanilla one, it is quite probable that Skyrim will ctd due its inability to purge the memory entering Whiterun worldspace. Only way to avoid this is to create a "jump point" cell between the interior and worldspace to purge the memory.

I see, for example exiting into bannered mare from my house and then leaving into town ?
What about making my exit maker outside the city ? just copying breeze home and placing it outside of town beside the stables for example ? it shouldn't cause any problems should it ?
And thanks alot for the reply

Ok another issue is that my followers won't leave the house cell with me . . nor enter it, i bypass it with the moveto player command on the console but it still bugs me . . any idea why this is happening ?

use moveto to get the player outside of the house, then use game.fasttravel, to bring the player back into whiterun worldspace. followers will come along. followers do not come with you when you use moveto. they instead try to find a path along the navmesh on foot. so they are still following, just trying to do it manually by walking (usually hitting the wait command will let them regroup on you)