Is it depression?

[philg]

First of all, I’d like to say that I am only looking for serious answers and I ask that if you do choose to help me, you read all of it.
I am a 16 year old boy living in Canada and for the past three years I have been struggling with what I think is depression. I want to ask my mother or my doctor about my “problem” but I feel that they would doubt me because I am only 16 and because many teenagers feel sad during these years but not all of them are actually suffering from depression. In other words, I don’t think I would be treated as seriously as an adult would be.
Ever since the 8th grade I have been feeling sad and unlike myself. Over the past three years I have lost interest in many things I used to be passionate about and I have lost virtually all self-confidence which makes being a teen very hard. Three years ago I had a loud personality, I was outgoing and funny and when I woke up in the morning I would be excited to live another day. Now, it is completely opposite. I have very few friends because I just never talk anymore. I don’t have the energy to be outgoing and to go out with the friends that I do have. I have no motivation to do anything. I miss school all the time because I either fake sick or beg my mother to stay home.
I have thoughts of suicide many times each week and most of the time I can’t pin-point exactly why I am sad. There are some rare days where I do feel happy and I go out and do things but it doesn’t last very long. Also, I try to work-out 3 or 4 times a week to improve my health but of course, I usually only do it once a week because I lack motivation. Usually after working out I have a rush of happiness that makes me feel like I could do anything but that too never lasts long.
I have put off telling anyone about this for so long because I thought I would get over it and that it was just typical teenage behaviour but now I feel that I need help.
Please tell me if there is anything my doctor could do for me and if you think that this is actually depression. I don’t know what to do anymore.