I'm currently taking sertryline and promazine for depression and anxiety but I'm still feeling low with periods of high and stable mood?

Sxs. Was that high and stable mood or high and unstable mood? If you are experiencing agitation, sleeplessness, rapid thoughts, euphoria, rapid speech, increased energy level, restlessness - please notify your prescribing provider right away.
Talk to your doc. Talk to your doctor about your symptoms to see if an adjustment in dose of your medications is needed. He or she may consider other medications if an adjustment is not helpful.