I understand however there was a time when I would get heavily convicted of sin and I would repent of it.
Yes, the Holy Spirit does convict us of sin - in order to lead us to Jesus so that, after repentance, we have forgiveness.
This lead up to me reading up the Bible and then I repented of my sins permanently(at least I thought it was) and put my faith in Jesus.
It may be controversial, but I don't believe we can repent of future sins.
We repent, which means turning around - we make a conscious choice to turn away from sin and towards Jesus. But we are still human, may be weak and live in a fallen world; sometimes we sin again. When that happens, we need to confess again and be made clean. Trusting in Jesus doesn't mean we'll never sin again, it means that when we do, we have someone who understands, intercedes for us, 1 John 2:1, and can, and will, forgive us again, 1 John 1:9.
So when we sin after becoming a Christian, it doesn't mean we weren't saved before, weren't "doing it right" or anything else; it means that we already know the Saviour, who died to reconcile us to God, and know where, and how, we can find forgiveness.
But eventually there came a time when I started to fight my convictions...
Do you mean that you were fighting the conviction that God wanted you to repent and come to him?
Again and again and again thinking that God would chastise me and stop me.
God had convicted you and shown you that what you were doing was wrong.
But he also created you with a will, and mind, of your own. If you know what is right but continually fight the urge to do it, why expect God to jump in and force you back onto the right way, or make it impossible for you to keep committing the same sin? That's a bit like a teenager who falls over because he is drunk and then sits on the ground waiting for daddy to pick him up so that he can walk again.
You KNOW what you were doing was wrong, because you were expecting chastisement. Ask for God's help in stopping that sin, or being set free from its power, by all means - but don't continue in it thinking "I'll carry on until God stops me".
It kept going until one day my convictions just disappeared and I was right back into my sin.
That's not surprising. The Bible calls it hardening of the heart, and if it continues; if you constantly reject the prompting of the Spirit in all areas of your life, and continue to do so for years, a time will come when you no longer hear, recognise or respond to such promptings. That time has not yet come, because you're on here, writing about your sin and blindness and wanting to follow God again.
I was in a state of complete darkness, completely unaware of my sin.
You WERE - you don't seem to be now. Which shows that God has not given up on you.
You appear to have given up on yourself, and are giving reasons why your sin is too great, or that you, alone, are beyond God's help - but that is not true. Whether you are too proud, or too depressed, to be able to see it, is for you to say.
Until one day the veil was removed from my eyes and I saw how low I had sank.
The "veil was removed from your eyes" by God, who wanted to show you how low you had sunk, so that you could turn to him again and be forgiven and helped.