Seeing a Doctor about Depression

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I have booked an appointment today for the doctor as I think due to my self-consciousness and weight problems I have developed a mild form of Depression.
I find myself with no motivation, I have a emotional breakdown almost every night where I cry myself to sleep and then I wake up and cry again.
I mask this before I drag myself to school, which is extremely hard.
Some of my friends tease me about having so many days off school, but really i'm just suffering inside and it hurts a lot when they say that, even though I know i should be going to school more often.
The depression, I feel it IS mostly because of my struggle with my weight all my life that has gradually gotten worse and the stress and pressure that comes with grade 12 at school.

The only people that know are my 2 best friends and my mum. I'm to scared to tell anyone else.

I have been trying to SERIOUSLY lose weight since March.
I have tried eating healthy, exercising at the gym often, Lite N Easy, a dietitan and nothing has worked. I have stucked to all of these and still lost nothing.
Im staring to think something is wrong with my body. Whether physically or emotionally, something is causing my body to hold onto my weight, as there is no possibly way that I couldn't be doing enough to lose weight.

I'm hoping my Doctor can help me out with this one.
It's probably the best thing I can do right now when I'm in this dark place.
I want to feel better and also start losing weight. Maybe getting this depression under control will help me.

I'm wondering if anyone has had a similar story to mine, and has done the same thing?