Why is Ranked so hard for me compared to Normals

I just recently started playing ranked after having my account lvl 30 for about a month but i am losing almost every game, i was placed in bronze and lose so much when i play but personally i dont think im that bad. So far i have won 3 games and lost 16 and i feel like i dont have any control over whether i win or lose. When i play normals on the other hand it seems incredibly easy. On my op.gg for the last 15 games on normals I have a 70% win rate and a couple of the games i lost i got fed but couldnt carry, while ranked i have a 20% win rate and have only done especially well on one game and feel like i cant make a difference on a lot of other games. Am i playing against worst players when I play normals or are they just not trying as hard? One thing I am trying to work on is maining one champ because up to this point I have been changing champs almost every game.