Is it sin to commit suicide?

Suicide is only for fools who do not believe in the power of God. In this world, we will experience tribulations. Things that make us feel uncomfortable are all around us. You are not the only person troubled.

JOHN 16:33
These things I have spoken unto you, that in me ye might have peace. In the world ye shall have tribulation: but be of good cheer; I have overcome the world.

Statistically speaking the incidence of suicide is constantly rising.

The World Health Organization (WHO) estimates that each year approximately one million people die from suicide, which represents a global mortality rate of 16 people per 100,000 or one death every 40 seconds. It is predicted that by 2020 the rate of death will increase to one every 20 seconds.

The WHO further reports that:

In the last 45 years suicide rates have increased by 60% worldwide. Suicide is now among the three leading causes of death among those aged 15-44 (male and female). Suicide attempts are up to 20 times more frequent than completed suicides.

Although suicide rates have traditionally been highest amongst elderly males, rates among young people have been increasing to such an extent that they are now the group at highest risk in a third of all countries.

Mental health disorders (particularly depression and substance abuse) are associated with more than 90% of all cases of suicide.

However, suicide results from many complex sociocultural factors and is more likely to occur during periods of socioeconomic, family and individual crisis (e.g. loss of a loved one, unemployment, sexual orientation, difficulties with developing one's identity, disassociation from one's community or other social/belief group, and honour).

http://www.befrienders.org/suicide-statistics

I can say with confidence that my problems and responsibilities are much greater than most people I know, but I live in hope because I have trusted that what I cannot do can be done by my great God. He is greater than everything in this world.

1 JOHN 4:4
Ye are of God, little children, and have overcome them: because greater is he that is in you, than he that is in the world.

Maybe, you cannot see God but, He moves people and makes them instruments of His goodwill to help someone like you.

Believe in the power of prayer! Pray and you will find peace and solutions to your problems — whatever they may be.

REVISED STANDARD VERSION
PHILIPPIANS 4:6-7
6 Have no anxiety about anything, but in everything by prayer and supplication with thanksgiving let your requests be made known to God.
7 And the peace of God, which passes all understanding, will keep your hearts and your minds in Christ Jesus.

Committing suicide is idiotic. Normally, in all aspects of life, even in lower forms of being, like animals and birds, life is being defended and preserved. The ability to adapt oneself in an environment and special defense mechanism are present in almost all forms of life: teaching us that the preservation of life is a will of the divine Creator.

It is only God, and God alone, who has the unquestionable power to take life.

DEUTERONOMY 32:39
See now that I, even I, am he, and there is no god with me: I kill, and I make alive; I wound, and I heal: neither is there any that can deliver out of my hand.

He allows nobody to take life! A murderer, He condemns.

1 JOHN 3:15
Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him.

He does not allow anybody to take life from another human being, regardless of the intent or the excuse, anybody may assert. Even mercy killing or euthanasia is not an excuse.

God is most merciful.

PSALMS 103:8
The LORD is merciful and gracious, slow to anger, and plenteous in mercy.

To say that anybody is killing anybody because it is an act of mercy, is tantamount to claiming that you are more merciful than God — and it is foolish.

God deals with people not only in this life, but through the hereafter, and no human perception can see what God has in store for anybody. He may let somebody in this life suffer a little but, there is reserved for him: Happiness in that which is to come.

1 CORINTHIANS 2:9
But as it is written, Eye hath not seen, nor ear heard, neither have entered into the heart of man, the things which God hath prepared for them that love him.

REVELATION 2:10
Fear none of those things which thou shalt suffer: behold, the devil shall cast some of you into prison, that ye may be tried; and ye shall have tribulation ten days; be thou faithful unto death, and I will give thee a crown of life.

REVELATION 21:4
And God shall wipe away all tears from their eyes; and there shall be no more death, neither sorrow, nor crying, neither shall there be any more pain: for the former things are passed away.

And He that promises all these things can not lie.

TITUS 1:2
In hope of eternal life, which God, that cannot lie, promised before the world began;

Lazarus suffered all his life. Nobody on earth knew then what is in store for him, but it was revealed in the afterlife.

LUKE 16:19-25
19 There was a certain rich man, which was clothed in purple and fine linen, and fared sumptuously every day:
20 And there was a certain beggar named Lazarus, which was laid at his gate, full of sores,
21 and desiring to be fed with the crumbs which fell from the rich man’s table: moreover the dogs came and licked his sores.
22 And it came to pass, that the beggar died, and was carried by the angels into Abraham’s bosom: the rich man also died, and was buried;
23 And in hell he lifted up his eyes, being in torments, and seeth Abraham afar off, and Lazarus in his bosom.
24 And he cried and said, Father Abraham, have mercy on me, and send Lazarus, that he may dip the tip of his finger in water, and cool my tongue; for I am tormented in this flame.
25 But Abraham said, Son, remember that thou in thy lifetime receivedst thy good things, and likewise Lazarus evil things: but now he is comforted, and thou art tormented.

Considering all these, and the dignity of the one who promised all these things, there is not an iota of reason for you to commit suicide.