What natural supplement is safest to take to improve concentration and stress while it doesn't interact with my existing med prozac (fluoxetine)?

None: Depression may be the cause of your lack of concentration. Speak to your doctor about possible adjustment of your prescription medications.

Supplement ; therapy: Rhodiola rosea is a natural supplement that people with add/adhd when they cannot tolerate amphetamines. You could try this. It will help tremendously if you also get psychotherapy for your anxiety which the contribute to your poor concentration, besides the prozac, (fluoxetine) which sounds like it s being used for your ocd.