If you are suffering from stress, then the best solution, in my opinion, is to go into therapy. You can learn coping skills that will help you handle stress better.
The best natural stress relief supplement with the least amount of side effects would probably be L-Theanine in my opinion. There are other natural supplements but they have more side effects and interact with a lot of medications.
st johns wart is a herbal supplement said to be used to balance moods over time, i'd ask a pharmacist before use.
Have you been diagnosed with depression. Does your doctor say you are suffering from stress not depression?
Ask at your local Health food shop what they recommend for stress, or the pharmacist at a chemist.
I have taken Calms before, but it takes like two weeks to take affect and I didn't find it all that useful. Honestly? You''re doctor is the best person to help you deal with this. Better still, find the source of your stress and try to come up with a solution, I know it's hard as everyday life is full of stress!
Talking on here, venting in journals etc might even help. This place is full of useful advice!