What if i'm already on zoloft (sertraline) & have been for years (50 mg) but now it doesn't seem to be helping at all & i am seeing that i must be very depressed. ?

Need change: After your doctor decides nothing else is causing recurrence of depression, a change in dose might be useful. You definitely want to let your doctor know about this so that he/she can help you.

Zoloft (sertraline): Talk to you doctor about possibly adjusting the low dose or other add on alternatives.

DOSAGE SUPER LOW!!!: I would speak with your physician because the dose you are on is super low so there is a lot or room for adjusting and augmentation with other meds. Have to see why there is a dip in mood after all these years as well so really need to speak to your doctor.