It does no good to whine to your manager about being short-staffed/overloaded/burned out. You need to provide evidence...metrics in other words...to support your case.
Think you've got too many IT helpdesk cases open? Fine. Start tracking how long it takes between the time the case is reported until it gets resolved. If you don't have some sort of automated system to track help desk tickets then chances are that it's getting buried in email messages. Let's say that the average time to close is 8 hours.
Now you've got something concrete that you manager can understand:
1) We need a system to properly track help desk tickets and somewhere to put the solutions so that we're not reinventing the wheel every time an issue comes up. Do a little research on what's out there and make some recommendations.
2) You've established that it takes 8 hours to close a ticket. Is that level of lost productivity acceptable to your manager? What are the impacts? What can be done from an organizational standpoint to improve response times?
As others have mentioned, don't go to your boss with problems. Go with solutions to problems. Help your boss to decide which is the best solution and why. Then go out and implement it and come back later and show him/her the results. Having measurable improvements will make your boss look good to his boss. And it will make you look good to your boss.
It's all about building a case for what you want. If you just go and say "we need more people" the answer will probably be no. But if you identify the problem and come equipped with some potential solutions you have a much better chance of success.
Keep in mind that sometimes just adding more people will not solve the problem. It can even make it worse. Start by taking a look at the process and see if you can find a better way to do things. Would it help, for example, to ditch Exchange and go with Google Apps for your email and scheduling? That's one less thing to manage and it allows you more time to work on other tasks.