Crocheting a beanie and it has ripples?

I am crocheting a beanie starting on top with a spiral. I have been increasing my stitches by putting two stitches in every one stitch. Also, I started with a single crochet and did that for a few inches, then a double crochet for a few inches, and then a triple crochet for a few inches. I don't understand why it is rippling, and I haven't even started to make the curve >.