Suicide kills the physical body, but that is not the source of your pain. Your pain is because of your psychological condition. If you kill your body, your consciousness will continue trapped in your psychological condition, but adrift in the internal worlds, propelled by karma.
You have not experienced the second death. The second death is the liberation of the consciousness from hell, it is the moment the consciousness has been totally cleaned of karma and defects, and is released back into evolution.
Whatever pain and suffering you are feeling is only the beginning of hell. Suicide will intensify it millions of times, because suicide is a sin not only against oneself, but against the giver of life: divinity.
Right now, because you still have your body, you have an opportunity to avoid more pain.
I recommend that you contact a suicide prevention service, and start using the magic of the roses.
"Do not worry; cultivate the habit of being happy." - Samael Aun Weor