I do know what you're talking about. I've been there. There's always hope.
We have the natural world to look to. I believe that it affirms the idea of a creator. Also, think of other things that we take for granted as existing, yet we can't prove, such as feelings and emotions. We can only see the effects of these things, not that they actually exist.
However, once you move past this, we can say that God exists and we can now 'see' Him due to the incarnation of Christ. Not only that, but baptized Christians who partake of the sacraments of Christ's Holy Church literally have Christ in them. It was seeing the risen Christ which convinced St. Thomas, after all.
Here's some quotes that I like, that hopefully you will get something out of too:
If you wish to save your soul and win eternal life, arise from your lethargy, make the sign of the Cross and say:
In the name of the Father, and of the Son and of the Holy Ghost. Amen.
Faith comes not through pondering but through action. Not words and speculation but experience teaches us what God is. To let in fresh air we have to open a window; to get tanned we must go out into the sunshine. Achieving faith is no different; we never reach a goal by just sitting in comfort and waiting, say the holy Fathers. Let the Prodigal Son be our example. He arose and came (Luke 15:20).
~Tito Colliander~ The Way of the Ascetics
The problem of our life is union with God, and sin completely prevents this; therefore flee from sin as from a terrible enemy, as from the destroyer of the soul, because to be without God is death and not life. Let us therefore understand our destination; let us always remember that our common Master calls us to union with Himself.
-St. John of Kronstadt (My Life in Christ, Part 1; Holy Trinity Monastery pg. 20)
Belief is a matter of dying for Christ and His commandments. It is believing that such a death is life-giving. It is to count poverty as riches, and to consider the lowest humiliation as true honor and nobility. Faith is believing that when one has nothing, one has everything. More than this, it is to possess the incomprehensible riches of the knowledge of Christ and to look upon all visible things as but clay and smoke.
~St. Symeon the New Theologian, The Practical and Theological Chapters
God is comprehensible in our contemplation of His attributes [or divine energies], but God is incomprehensible in our contemplation of His divine essence."
-St. Maximus the Confessor(Cent. On Charity, IV, 7, trans. Pegon, Sources
Chretiennes 9, p.153)
But some one will say, If the Divine substance is incomprehensible, why then do you discourse on these things? So then, because I cannot drink up all the river, an I not even to take in moderation what is expedient for me? Because with eyes so constituted as mine I cannot take in all the sun, am I not even to look upon him enough to satisfy my wants? Or again, because I have entered into a great garden, and cannot eat all the supply of fruits, would you have me go away altogether hungry? I praise and glorify Him Who made us; for it is a divine command which says, 'Let every breath praise the Lord' (Ps. 150:6). I am attempting now to glorify the Lord, but not to describe Him, knowing nevertheless that I shall fall short of glorifying Him worthily, yet deeming it a work of piety even to attempt it at all.
-St. Cyril of Jerusalem (Catechetical Lectures: Lecture 6 no. 5)
"For behold, all our lofty doctrines, how destitute they are of reasonings, and dependent on faith alone. God is not anywhere, and is everywhere. What has less reason than this (What idea makes less logical sense)? He was not made, He did not make Himself, He never began to be. What reasoning will receive this if there is no faith?"
-St. John the Chrysostom
Abraham passed through all the reasoning that is possible to human nature about the divine attributes, and after he had purified his mind of all such concepts, he took hold of a faith that was unmixed and pure of any concept, and he fashioned for himself this token of knowledge of God that is completely clear and free of error, namely the belief that God completely transcends any knowable symbol. And so, after this ecstasy which came upon him as a result of these lofty visions, Abraham returned one more to his human frailty: `I am,' he admits (Gen. 18:27), `dust and ashes,' mute, inert, incapable of explaining rationally the Godhead that my mind has seen.
-St. Gregory of Nyssa, From Glory to Glory
Before anything else one must believe in God, "that He is, and that He is a rewarder of them that diligently seek Him" (Hebrews 11:6).
-St Seraphim of Sarov - Spiritual Instructions
Preview of "A Pilgrim's Way" Orthodox documentary - YouTube