I have installed new vegas to my hard drive, downloaded the dlc deleted it and reinstalled it, and every time, when I get knocked out it freezes... im sad and angry

Did it work before you deleted it and reinstalled it? Or was that the reason you did so?

Have you attempted to play it from a different save (assuming you have more than one)?

Have you tried clearing game/system cache?

I have tried all those things except clearing the game/system cache which I do not know how to do.
(I have fallout for xbox 360)

I don't either, but there's threads on it/googling it will help. I've never had to do it. Clearing game cache is something about holding left bumper, right bumper and X while the game is starting or something, and clearing system cache I think is inside the system settings.

I have just tried it a few minutes ago on several different saves, and redownloaded the dlc... still nothing

I just switched hardcoe off and changed easy to hard to make up for it,
hardcoe mode is glitching it up, do your achievements and take it off

I've never used hardcoe mode so that may explain it. You can also try turning hardcoe back on (assuming you already have the achievement, and if you don't it's a little late now anyway) once you're into it, to see if it'll let you continue (though you may not want to since there's already so few stimpacks around and apparently the air is constantly toxic no matter where you are in hardcoe mode)