No, not stress testing, testing stress.
Stress is an unavoidable part of quality assurance if you're doing QA right. You're responsible for the end quality of the product, but you don't have any of the means to effect change beyond your bugs. Being responsible for something you really have no control over is always stress-inducing, but when that describes the entirety of your job, the stress can be overwhelming at times.
Every tester has different ways of handling the stresses involved in testing...some healthy, some not.
When I first started testing, the exhiliration of being in the games industry masked the stress enough that I didn't notice it. Around year two, whenever the stress got too much, I'd constantly mutter, "I'm gonna quit, I'm gonna quit, f*ck this job, etc." under my breath. By year three, that had involved into a biting sense of humor, with some dangerously sharp jokes in my arsenal. Year four, relaxing baths. Year five, the amount of stress finally outpaced my ability to handle it.
Of course, that was back at Microsoft. The studio I was in didn't seem to acknowledge that work/life balance is a key component in any job.
I'm in my seventh year in quality assurance now. I do my best to limit my overtime to reduce the amount of stress that I'm under. My office is filled with items that soothe my spirits. (I doubt they'd help anyone else, but they help me.) I spend a lot of time walking and listening to music to wash away the stress I've got.
Some days, like yesterday, the stresses of my job and life combined get to me, and I find myself reverting to some of my older techniques to try to further decompress. On other days, work goes so swimmingly that it reduces my stress for me. Regardless, stress management is one of the hardest parts of being in quality assurance (and the games industry as a whole), and everyone needs to handle their stress differently.
If you find that stress is getting the better of you, or if you exhibit multiple symptoms of stress, try to handle it as quickly as possible before nasty physical side effects sideline you.
Talk to your manager, talk to a psychologist, talk to you wife, talk to some stranger sitting next to you on the bus or train, blog about it to the world. The important thing is to talk it out, because stress can only damage you for as long as you keep it inside.