Based on my own experience, I would say that you are keeping your head down for too long. You need to look up every few seconds to check the horizon.
I remember in my cross-country training I became obsessed with the paperwork and when I finally looked up I discovered the aircraft had gently rolled into a 30 degree angle of bank. I blurted out an obscenity, my instructor laughed and said he'd been wondering how long it would take me to realise what was happening.