Help me....

Something's wrong with me....
I don't know what it is, or what's causing it, but something is seriously wrong with me.
I'm being nasty, telling people to fuck off, getting frustrated at tiny little things, taking huge mood swings that range from paranoia to pure anger, the only thing that doesn't change is how depressed I feel...
To make it worse, I'm taking it out on a lot of people without even realising, especially Michelle, and then when I realise I'm acting like a retard, I feel even more depressed cuz I'm sure I've hurt her and possibly a few others as well, and then I get more frustrated at something stupid and that leads to more anger and that leads to more depression and It just wont stop, it hasn't stopped for a few days now....and it's hurting...
Fuck, I acted like a prick earlier and ended up punching the wall cuz of it, which really fucking hurt, that was about 7 hours ago, still hurts a lot, painkiller appears to have done fuck all too, which is frustrating as hell...
The mood swings are the worst, one second I'll be happy and fine, then Michelle will say she's going to play VC (Vice City) or something and I'll freak out thinking she just doesn't want to talk to me and is making up excuses, and end up saying something nasty then piss off offline, only to realise a few seconds later what I've just done and feel shitty as hell about it, then the paranoia starts to come back, I'll start thinking that she's gonna get fed up with me acting like this a leave me, which actually is starting to feel that way since she's been a lot less....I duno, just not as close as usual, but then I could be just thinking that cuz of this annoying paranoia that keeps hitting me every now and then...
I want it to stop, I want it to be back to normal, where I'm the jolly fat Irish dude and not the manically depressed guy that hasn't tried to "make things better" only because of a promise he made to someone back in december....
I feel like I'm standing on some sort of line, so so close to falling off the edge, wanting to fall of, but there's a string, a promise, keeping me on it, just barely on it, but still on it...just...
I need this to stop before the string breaks............