“What are the symptoms of depression?”

They very from person to person & include depressed mood and/ or loss of interest of plessure, changes in appetite, sleep, energy; changes in attention/ concentration; guilt/ worthlessness/ hopelessness; and suicidal ideation (thoughts). Meds & therapy can be VERY helpful and there is much reason to be hopeful.
If you have suicidal thoughts you need to notify your psychiatrist & therapist right away. If imminent, you need to call 988 (national suicide hotline 24/7), 911 or get a ride right away to your nearest ER. Of the latter 2, it's often better if you can get a ride.
Caution about 988: colleagues from other parts of the country have complained that there aren't enough treatment resources for prompt treatment. I honestly haven't had a chance to check it out here in San Diego & have some more portal questions to answer first.
Have a blessed day.
If you have suicidal

Core symptoms of depression include:
Sad, irritable or bored mood, loss of interest in things that give you pleasure, changes in sleep, appetite, energy and concentration [typically worse], feelings of hopelessness, helplessness, guilt, worthlessness. In more serious cases, it can be associated with thoughts of death, suicide and some patients even experience auditory hallucinations [typically of their own voice telling the negative things about themselves]. I would follow up with you PCP- he can complete a simple questionnaire that can assess your level of depression and talk to you about options.

Lack of energy, sleep disturbance, irritability, feeling "blue."

Sad mood, feelings of hopelessness and helplessness, anhedonis (meaning low energy), poor sleep, weight change (gain or loss), intrusive thoughts about being worthless, etc. Please see a psychiatrist ASAP.

That can differ with individuals. Basically sad with your life and family. Like being by yourself all of a sudden. But it goes beyond all that

Depressed mood most days, loss of interest or pleasure,weight loss or gain, insomnia or over sleeping,agitation or retardation, fatigue or loss of energy, feeling of worthlessness, decreased ability to think or concentrate,;and thoughts of death or suicide. At least 5 of these symptoms and decreased functional ability. If you are close to this symptom cluster, you should seek a comprehensive evaluation.

See this link:
dailyhealthlifestyles.com/9-5-2016-11-early-signs-of-depression/?utm_source=symptoms%20of%20depression&utm_medium=depressionsigns&utm_campaign=bing