Maybe. Maybe you're just knackered? Or suffering from a vitamin/mineral deficiency?
Being depressed is different from normal feelings of sadness, grief, or low energy.
Common symptoms include; trouble eating (or eating too much), sleeping (too much or not able to?), anxious, tearful, feelings of hopelessness, pessimism
worthlessness, helplessness, losing interest or pleasure in hobbies and activities that were once enjoyed, including sex, decreased energy, fatigue, difficulty concentrating, remembering, making decisions, thoughts of death or suicide; suicide attempts, Restlessness, irritability.
Persistent physical symptoms that do not respond to treatment, such as headaches, stomach disorders. etc.
If you think you may be depressed, you could ask your gp.