I’m sorry you’ve gone through what must have been an absolute agony
I really recommend speaking to a good priest. There are various things that this could be. The dark night of the soul, is given to souls who have already gone through the illuminative way and are almost Saints. The dark night leads them into the “spiritual marriage” state of soul. What is more common is the dark night of the senses, which happens somewhere before the illuminative way, and leads into that state from the purgative way. Books like the “three ages of the interior life” can help
christianperfection.info/index.php
The dark night of the senses is when a person doesn’t feel God’s presence or any consolations in prayer. Dark night of the soul, - I think it happens very rarely. Then there are also trials that are the result of our own lack of prayer or unrepentance. But if you were living a good Christian life when all this began, it’s likely to be another sort of trial. Extreme darkness can also be some sort of an attack too, in other cases. I’m just talking about everything here that is spiritual. A good priest would be able to help you figure out what maybe happened…
but I think whatever it is, it is very important to rely on your will instead of your feelings. St Ignatius of Loyola said to never make decisions at a time of “desolation”. So if when you felt differently, you decided to follow Christ, and then later you started going through this darkness, the important thing is to just persevere through your decision. The darkness doesn’t last forever. God could use it in some way and then take it away. I know it’s very very painful though. I’ve gone through times of strong spiritual darkness and it IS very hard to go through. It never lasts indefinitely… we just need to persevere. If you left the faith for a bit as you said, don’t get discouraged about that either, but just come back and keep going.
I think that often, God can use times of darkness to help us to learn to love. Our Lord cried out on the Cross “My God, My God, why have You abandoned Me?” yet He continued to love. Of course, He is God and He is perfect… but often in trials, we learn a lesson of what love means. It is simply in the will. When we feel consolations, we might love God because of them. In darkness, if we make acts of love towards God, that can even be heroic, we can even become a Saint through this. We show true love then. We all fail in this… it’s important to just keep going and trying.

ask Our Lady for help too. God bless you!