People who have never been depressed dont understand what it actually means beyond "feeling down" unless they've had experience with sufferers of chronic depression.
Depression isn't something that happens overnight, its not something you wake up with one day and think "oh, I'm depressed" it literally creeps into you over a long period of time and slowly takes charge of everything.
Its not a normal change of mood that everyone in the world feels from time to time, its a complete change of out look on life. Its like a disease that eats away at your pattern of thinking and choice making. You dont sit down and think, right, I'm going to be miserable and not do anything because I feel sorry for myself. Its not like that.
Its not a matter of just "doing things you enjoy" because you dont enjoy anything. For me it was like I had systematically cut-off all reason for doing anything to the point of feeling like a walking corpse. It was a complete self-destruction that lead to some really horrible experiences, yet all the while, I felt as if I was in complete control of myself and my thoughts, but I just couldn't see the blazing black hole that was inside me making me feel like a rotted zombie.
The best way I can describe deep depression is like this:
Imagine a prisoner, someone being kept indoors and told to take medication that numbs them, destroys their emotional rationality, their desires and all sense of self worth and confidence.
As time goes on he rots, becomes frustrated, thoughts are filled with death and he finds it increasingly harder to find reason to breath. The slightest thing can knock him down as if the weight of the world is on his shoulders.
Now consider that this person is the jailer himself and that he completely 100% believes that this medication is good for him, so he keeps taking it, even though its destroying him.
Fortunately things can only go up from there once you realise that the 'medication' (the change in your personality) is actually a freaking disease and that other people are feeling exactly the same. I struggled about going to the GP for weeks after I realised that I was in a seriously bad way. In the end I felt as if I had reached the ends of the world in terms of emotional rape so I had nothing to lose and just made myself goto the doctors early one morning. I was swetting, panicking and looking at the exit door as if it were a fire escape... but I done it.
That was 4 years ago, and it was the best decision I've ever made. It really has been uphill since. So if anyone is still wondering about going to the GP about their feelings then all I can say is, for the love of God go now, today, talk to them. There are SO many sufferers from depression and its a very common disease and doctors see this all the time. They're not going to sit there and judge you, they're there to put things right. You just need to take that first step and you'll feel as if the worlds weight is removed from your shoulders.