There are different ways to force yourself to be host such as joining and rejoining TDM and then finally letting it search for a few seconds. This method also works well if you have friends on your list join you at the same time as you do this. Lastly look up a MW2 force host tool, on Google you can find other methods, exact tools, line of code to create your own tool / DLL and lastly even note pad scripts to make you lag in order to gain host.