Photoshop brush acts like eraser photoshop for iPad

My brush tool acts like an eraser. This happens across all my photoshop documents (i.e. it is not an issue with adjustment layers etc.) and I have tried resetting brushes and changing the foreground and background colours. I have photoshop for iPad version 3.6.3 . I think this happened because I used a touch shortcut, but when I stop using it and it says 'paintbrush' in the corner of my screen, it still doesn't work. Similarly when I use the touch shortcut to get my eraser to turn into a brush, it continues to erase.