zarqoun, I am sorry you are feeling like this. I haven't got to the point of feeling suicidal, but I have felt like I was having a nervous breakdown, and I have got to that gut-wrenching, desperate I can't stand any more point.
One thing that helped me was understanding that it wasn't me failing or being pathetic. The origins of that massive panic state are quite simple and universal: you are under threat, your body and mind experience the 'flight or fight' instinct, but you can't fly or fight, so you are left with a huge terrible overload of panic instead.
IME, powerful feelings of stress are quite common among people dealing with difficult teens. You are put into 'flight or fight' mode frequently - often many times a day - and you can't run away and abandon your kids, or knock them down, even though that's what your instincts are pushing you to do. Often, just as you start to relax slightly, there'll be some other incident, and your stress levels rocket again. Your adrenaline and anxiety levels stay high, and you feel permanently 'wired' and often a bit unreal.
Ironically, I think people with good self-control suffer most. If you lose so control and do one or some of the things that society tells us make us 'bad parents' - shout or scream or hit or storm out - then at least the 'flight or fight' impulses have had some release, though the problem won't be resolved. Those of us who don't do these things - who stay outwardly calm - have no such release.
You may be able to 'go on going on' for a bit longer. Most of us dealing with troubled teens cope with very, very much more than we ever think is possible. But if you have reached the point of suicidal thoughts, you are past any reasonable limit. Don't let yourself go on coping alone. Please get some help.
I really do understand the feeling that there IS no help. I ran around frantically trying to get anyone at all to help, and didn't have much luck. But keep trying. You will find it helps even to try, I think because you get at least a bit of that release of tension I described above.
I phoned parent line, now called Family lives on 0808 800 2222. They have web chat too. They weren't phased by me weeping and railing down the phone, and they sorted out some useful regular phone counselling for me quickly, which saw me through while I waited for a GP referral.
Also, do something nice for yourself. I say this a lot here, but it isn't a luxury: it's a survival essential. It will help 'balance out' the sh*t you're dealing with, just a bit.