Do you have access to your web logs? If so, you can use something like awstats or another utility that your web host should be able to provide to give you usage data. You can use a third party such as google analytics if you want. http://www.google.com/analytics/

Do they give you control over who can access what? If so, you can block them by ip, netblock. Who is your web host and what kind of interface do they give you to manage your site?

If they refuse to help you or don't give you the tools to do it on your own, then get a new host.