Depression Support Group
Depression is a real and debilitating condition that is often misunderstood by family and friends. Its meaning can range from a prolonged period of sadness to an actual mental illness with specific symptoms. Find and share experiences with others who are going through the same struggles.

In the easy times, and perhaps in the harder times, an untrained friend or family member can be a huge help. (My wife was just such a help when I finally admitted that I was not happy.) But it can really take professional help to deal with the hard times.
And it can take professional help to formulate a plan that can help with the overall approach to his depression.
I liken depression to being diabetic. All diabetics need to monitor their diet and be aware of things that indicate their sugar levels are out of balance. Some, not all just some, diabetics must take insulin, others may need it infrequently.
So for a depressed person, therapy is our "monitor our diet". It is the common thing that we all can benefit from.
So for a depressed person, being aware of our triggers (for example, some depressed people suffer a lot during heavy rain storms) is like a diabetic knowing that certain things mean their sugar levels are off (thirst, being light headed, blurred vision are examples I learned from WebMD). Then the depressed person can take evasive actions. Avoiding triggering situations when we are already anxious is good, focusing past short term situations is another coping method.
So for a depressed person, medication may be required to manage our symptoms. Just like the diabetic needs insulin on a regular basis.
All of these things require professional help to get started, I mean to get a good start. A lot of us here have gone through that, but none of us here, that I am aware of, are professional healthcare people specializing in depression. So our help is a good guideline, but we often miss subtle yet important aspects of specific cases that the professional is trained to look for.
Please listen to the others here when they advise you to set limits. Do not become the only thing that keeps your BF going, that is a situation that almost never ends well. You can be part of his support network, you can even be the largest non professional part of it, but once you become "it" he stops relying on himself. And in the end, we all need to be responsible for ourself.
Sorry to go on and on, ...
Gentle hugs
It is hard to walk alongside someone who is struggling and not being able to change it for them. Make sure that as you walk alongside your boyfriend, that you are also seeking help for yourself, whether through supportive friends or a counselor that can help you through this really emotional and difficult time. Keep going strong!