Have you seen a doctor about these symptoms? If it is interfering with your life, personal relationships, causing you to harm yourself, none of that is normal. You need to talk to your doctor about this to rule out any possible medical causes. If it is not something medical, ask to be referred to a psychiatrist.
The extreme highs and lows might point to bipolar disorder, rather than just depression. When you see your doctor, mention all your symptoms, not just the depressive ones. Too often, people with bipolar disorder get diagnosed with depression. It takes, on average, 10 years for someone with bipolar disorder to get properly diagnosed. Treatments for depression will not work on bipolar disorder.
The reason I said that you should be treated by a psychiatrist, rather than your regular doctor is because primary care doctors don't have enough experience in treating things like bipolar disorder. They may not know the most recent medications and studies that have come out. You also may need talk therapy in addition to medication, which your regular doctor can't provide.
You know that something is wrong, otherwise you wouldn't be writing this. You aren't happy with the way things are. You said this has been going on for years, so it isn't going to get better on it's own. There is no shame at all in seeking help. You didn't cause this, there was nothing you could do to prevent it, but you can take steps to make it better by going to the doctor.
I wish you all the best. Good luck.