03 intermittent starting problem

My 03 has been having intermittent starting problems, but has always started up after a couple of tries. However, today it is not. It turns over, but won't start up. The check engine light is on, though I know I have an o2 sensor acting up, that triggered it a month or two ago, and I have yet to fix. Not sure if the engine light is related.

I recently put a new battery in (about a month ago).

This intermittence has been occurring for a couple of months.

Any ideas?

Thanks!

ok, so now the car won't start. I took the battery in to Advanced, they checked it, and it was fine. starter?