Who can i tun to? Help with depression?

Hi there
This may seem a random qyestion but i need helpd. This past 2 months i have had no energy to do things, i feel as if i cannot be bothered to do anything (This is awful as i have 2 jobs)
I still come to work but i find it a challenge to find motivation.

When colleagues ask if im fine i often make up pathetic excuses to either avoid the question or to try and convince them im fine.

I did have a moment when i seemed happy, i met this girl (We were great friends and wanted to take things further) Rookie mistake right?
Basically i asked her out and she said yes.A Few days later she basically said she cannot be in a relationship with me and is 'sorry'for messing me abiut. But now it seems mybest friend is on the scene and they are always flirting andmeeting up, yeah i know it sounds a LOT like jealousy but that has set me right down, i often try to avoid conversation with her on Facebook/text.

But this past 2 weeks iv felt really down, iv not been eating properly, my mum has picked up on me not eating meals.

The worst part is i have a penknife (I use ot for my bike and if i go camping). I have often found myself slowly sliding the blade over my skin, not cutting but scratching the skin.

What cn i do...I dont want to tell my friend/fmily what im going through, i dont want to worry them...

This seems to be the only way i can vent my feeling

Thanks guys...