I have a cyclecross bike that I use for commuting. I converted it from a 18 to a 9 speed and am having trouble keeping the chain on when I am in the lowest gear. The chain moves off the gear towards the bottom bracket.

I have seen 1x9 speed cycle cross bikes before, so I figure this must be possible?

My chain-ring is quite worn, and I plan to replace it soon. I am wondering if the worn chain-ring could be to blame for the derailments? Or should I just convert it back to 2x9 speed?