I grew up with depression and it took me 22 (almost 23) years to even get stable enough to socialize normally with people.
First off, you HAVE to figure out what's bugging you or what your triggers are, at the very least, before you can really get any better. Night? Day? A certain person? Certain activities? Certain places? You say that it happens around this time every weekend and that leads me to believe something happened a while ago repeatedly on the weekends that scarred your mind to the point of just automatically feeling like shit on weekends. It happens to more people than you think. I also read a comment of your's here saying that your room is a mess. That, alone, is enough to drive some people into some really dark places.
Also, in my own personal experience, "not thinking about it" is about the worst possible thing you can do. You'll still get wet if it's raining even if you don't think about it. It's better, sometimes, to do some thinking on it. I might warn you that you can be "alone" doing this, but if something snaps, you'll want someone at least in the same house for you to go to, or to stop you from doing anything drastic. So I would advise that you be alone in a different room, but not alone in your whole house.
On the other hand, trying too hard to figure something of this nature out can be just as, if not more damaging than the whole reason itself. It's a fine balance, and I would advise you to start slowly with it. For me, "slowly" was 2 hours per week in therapy and just trying to keep myself busy otherwise.
Getting control of depression if not an overnight thing. Sometimes, it can take a couple of months. Sometimes, a few years. It personally took me 7 years of therapy, 4 stays in mental hospitals, 6 different therapists, and 4 different psychiatrists just to get to where I am.
That being said, it really sucks to hear of someone else going through similar problems of mine. I wish you the best of luck, and do keep your head up. (Keeping your head up can actually help your mood. Ironic.)
tl;dr There isn't a tl;dr. You pretty much have to read this to understand it fully.