For some weird reason, whenever I go onto Krita (2.9) I can draw on Layer 1 (with the white background) but can't draw on Layer 2 or any other layers I create with a transparent background. Also, when I erase something on a white background, it becomes transparent and as such I can no longer draw on that particular area. I don't think I pressed any weird keys, and I haven't messed around with the files. What's going on??? If this continues then I'll have to stick to one layer

Make sure you're not painting with alpha-lock on. That's the checkered box in the toolbar.