You'll hear about lots of different therapies, many of which involve relaxation. Many of these therapies involve other elements, for example reiki works with the body's energy fields, and this may be of interest to you, but even if it's not, you might find the relaxation side useful.
These types of methods and therapies include reiki, reflexology and various forms of massage. Do some research, read about different therapies, and maybe visit a local clinic to find out what's on offer and find the most suitable treatment for you. Some of the less "alternative" therapies include jacuzzis, steam rooms and spa pools. You may also have heard of flotation tanks, also known as sensory deprivation tanks, which can be very effective, although you may find that a nice hot bath also does the trick.
Stress is a medical condition and it can have a serious effect on your health. If you think you are suffering from stress it is crucial that you consult a medical professional.