Well I don't think it was casting on that was the problem. I even redid it three times to make sure. So maybe I am pulling the yarn too tight like you said. I didn't think I was, but since I'm not used to the yarn I'm using or the size of the needles I might be just messing it us as a result.
So I'll give it another shot! I got mad and stopped for a few days, but I really want to make this. Worst case scenario I'll ditch trying to knit it and croquet a blanket instead, lol.
Thank you for the advice! <3
Oh, and I'm using needles that are made out of some kind of plastic, not wood or metal.