Hi there   You ask a good question.  I fear that only a therapist could accurately diagnose you for depression.  Stress can definitely make depression worse...are you feeling stressed.  Are you feeling sad?  Is your eating or sleeping affected?  Exercise can help but it is just one way to combat depression.   Could your hormones be at play here?  I am just throwing out ideas.   Maybe what you could do is to write a symptom diary of how you feel each day and with concrete examples...like you are giving us here.  And then look for any patterns.  If you feel that things are getting out of control and you cannot manage...then perhaps it is time to think about seeking some counseling or even go to your general practitioner to rule out...illness.  I know sometimes thyroid problems, for example, can cause depression.   Writing in a journal is an excellent idea.    Some people use folate, Vitamin B-12, and fish oil to help their mood.   You are going through a major life transition...that can cause stress and feelings of depression for many people.   I hope this helps some.  Please let us know if you find something which works for you.  And thank you for your question!