We all know that when we are overwhelmed by stress on the job, then we've got a big problem that can be tough to manage. What most of us don't realize, however, is just how much stress there is going around among our co-workers. According to the American Institute of Stress, 80 percent of workers feel stress on the job, and nearly half of workers reported that they need help dealing with this stress.

And where does all this stress come from? The main causes of stress on the job are workload (46 percent), people issues (28 percent), juggling work and personal lives (20 percent), and lack of job security (6 percent).

Many of us know that, at its worst, stress on the job can result in high blood pressure and even heart attacks. But there are some unexpected and surprising signs and symptoms of stress that you might not even notice--until it's too late.

If you find that you're experiencing any of the following stealth stress symptoms, then it's time for you to track down the source of the stress you're feeling and address it.

1. Headaches

If you're like me, you've probably got a bottle of aspirin or ibuprofen in your desk at work. If you find that you're getting frequent headaches, the source might very well be the stress you're feeling on the job.

2. Feeling tired

You may not realize it, but stress takes a lot out of you--so much that you can feel very tired at work, even after a good night's sleep. If you find yourself drinking a lot more coffee to try to stay awake on the job, then consider the stress you're feeling and do something about it.

3. Back pain

Stress can cause us to tense our muscles for long periods of time. And when those muscles happen to be in our back, the result can be back pain.

4. Nausea

If your stomach is frequently upset--and your eating habits haven't changed lately--then consider the possible impact that the stress you're feeling on the job is having on you.

5. Frequent colds

While you might think the source of your frequent colds, bouts of flu, and other infections is your co-workers or even your kids, there's a good chance your immune system is being compromised by stress. If you reduce the stress you feel on the job, you'll boost your immune system, and those colds and other ailments will be significantly reduced.

6. Excessive sweating

Most of us are aware that we start sweating more when we get nervous--for example, when we're about to go onstage to speak in front of a group of 1,000 people at an industry conference. However, we may not be aware that we also start sweating more when we're suffering from routine stress on the job.

7. Loss of sexual desire

While there are all sorts of possible reasons for lessened sexual desire, feeling stress at work can be a major factor. When you remove the source of the stress you're experiencing on the job, you may experience a significant uptick in your sexual desire--and happiness.