Dylan, I lost count of the demons oppressing me in my teenage years when I turned 18. I shall never forget the torment my doubts, my despair, my anxiety caused me. I wouldn’t like to go into this now, but I just feel every word you post, deeply.
One thing that helped me, or at least made the whole thing bearable, was to stop fighting. Yes, you read that right. Do not fight, you are not able to carry your armour! What I sometimes did (when I had the time and the occasion) was lie down, even in the middle of the day, under a blanket, and rest - and pray in that relaxed state. As if I had been still a child.
Confession also helped. OK, this is personal, but there was a dreadful period in my life when I had serious doubts about life after death. The fear that nothing but annihilation is coming after death grabbed me and filled me with a cold despair. When I went to confession (I always confessed to the same priest, a wise, kind old Cistercian) I confessed this. And he was able to sooth me. After confession, mass began - and one of the readings (I forgot the exact passage) was about death and how it is not annihilation, but the gate to eternal life. At this sentence, he briefly but clearly, looked at me from the altar. Nobody noticed, except me - our eyes met and suddenly I felt comfort. It was a small morning mass on a Saturday. And I thought: if this old monk, with his seventy years of experience in faith and doubt, in joy and fear, is not afraid any more, surely I can believe him!! And surely I can believe the word of God!
Fighting against demons is hard. It is easier to fight for God, for he is near and willing to surrender. Rest, pray, and trust that God will fight for you.