All of my brushes act as if using a blend mode and i dont know how to turn it off

I've just been messing with some new brush sets and a few hours ago every one of my brushes started acting strange. Instead of adding the same color I have color picked from the painting, it's creating some sort of blend mode(multiply?) layer on top of wherever there is already paint. If I insert a new layer on top, I can paint one stroke of paint down and it will look normal on top of the painting(with the exact selected color) until I add another stroke over that piece on that same new layer, which adds the darkened effect yet gain. Opacity is 100% for all brushes here, each layer is set at "normal." I've hardly touched brush settings aside from brush size. Is there any way to turn this brush effect off for all brushes? 

I only just started using photoshop today coming from a much simpler program, Autodesk Sketchbook. It's very likely I bumped a key or something by accident and now I'm just stumped. Any help would be absolutely appreciated (: !