Sorry to hear about what you have been going through.
Ending any long-term relationship is a great loss, even if it is better for you in the long run. There is a normal period of grief which varies from person to person after many divorces, which is not unlike the death of a love one. You need to let yourself go through this process and experience all the emotions that go with it---anger, relief, guilt, anxiety, sadness--before you can move on with your life. If you feel that you have experienced these things and continue to dwell on certain aspects of your relationship, or regret going through with the divorce, then I do think there may be a deeper problem that needs to be tackled.
Was there anything that was especially messy about the divorce which you wish had been handled differently? Do you feel guilty about the effects the divorce may have had on your son? Has your life not gone the way you hoped it would since your divorce in terms of your career, starting a new relationship, or in terms of your relationship with your son? These types of things can lead to unresolved psychological roadblocks that sometimes need to be talked out with a licensed counsellor.
Your symptoms right now are also very typical for depression rather than just normal grief. In many cases, taking an antidepressant medication can help you "get out of the hole" while you also try to explore the underlying reasons for your symptoms with a good counsellor. You may wish to ask your doctor for a referral to a clinical psychologist or psychiatrist with expertise in grief counselling and depression, who may help you through this difficult period.
I hope this has helped.