In my experience, medication is a great way to give you the kick on to deal with the source of your problems. I ended up getting Fluoxetine a few years back. The lift I got from it was enough to allow me to take positive steps to change my life.
Since then, I have realised that depression is something I had lived with for a long time. I still get low, but by being able to spot what is going on, I have more chance of not slipping into depression, which is a hideous, crippling illness.
I view it in much the same way as physical illness like diabetes. It is something I live with, and I try to control the illness, rather than let it control me. The hardest thing for a person with depression to accept is that there is hope and they will get better - the very nature of it means that you take a pessimistic outlook on life.
When I am low now, I try to remind myself that I have been here before, and things will change. If you are suffering then don't hesitate to speak to your GP. Try and describe your symptoms: how are you sleeping; what is your appetite like; are you avoiding people that you like; do you feel like life is not living. There are also many great sources of advice on the net (as well as some dodgy ones). Here's a couple of links:
http://www.samh.org.uk/
http://www.moodcafe.co.uk/
Even looking at these means you are acknowledging your problems, and you have made a big step. One last thing, if you are drinking too much (as I was) try and cut back, and build towards a couple of days of sobriety - I also have serious doubts about weed. You'll be amazed how things come into focus, and also what a liar alcohol is.
Good luck, it's a long road, but you can get better. Sleep and nutrition are massive factors. One last thing, I found that just talking to someone made me feel a whole lot better.
I hope that's helpful, the rest is up to you.