Illustrator filling in areas of a path when "no fill" is assigned

I've had Illustrator for roughly 2 months, and this randomly occurred yesterday. Straight lines come out perfectly fine, but when I attempt to draw a curve it ends up becoming filled in, even when no fill is assigned. The filled-in portion remains when I remove the stroke as well. I'm using the Tapered Brush from the Artistic_Ink brushes in the Brush Library and a 0.25 pt stroke. I did some additional research online and the posts I found stated that this issue has been happening for a while, however, I haven't found any working solutions. I really hope I'm overthinking this or something. Any feedback would be greatly appreciated.