Will stress cause bipolar symptom to return even while on medication?

It's possible: Stress severe enough can cause someone with bipolar disorder to break through their meds. It is very important for someone with bipolar disorder to make sure they do as much as they can do to reduce mental and physical stress by making sure they get enough sleep regularly, eat healthy and regularly, exercise regularly-- in other words, take good care of themselves.

Yes: Stress and insomnia are two of the greatest triggers for relapse into bipolar disorder. You will need to see your psychiatrist asap and have your medications readjusted. Best wishes.