Penalizing Host

What are the chances of google penalizing your entire host and how would you know? Im probably being paranoid but every new site I seem to make doesnt seem to rank well. All of my old sites are ranking fine but everything new I seem to make doesnt.

You're probably doing something wrong. Can you give us more details? Like where are you hosting your sites, whether you've done on/off-page SEO...

Cutts has talked about this is more than one of his videos - the short answer is, it's very unlikely that every site hosted together will get penalized together.
The only time that would happen is if, for example, 915 out of the 920 sites hosted there were crap, then the other 5 would likely suffer collateral damage.

tony_d is exactly right. The only time they take such measure is when they know that the host belongs to one guy who is massively spamming. If you share the host with tons of sites, if Google started banning those, they'd miss lots of possibly good content.