If you feel you are not ready to make the decision, you aren't. It's that simple.
It was a very difficult decision for me. I filed for divorce 6 weeks after dday. It was not something that I wanted to do, but there was no chance for reconciliation. My WS chose to be with the OW. I listened to his actions rather than his words. To be honest, I did not want to get served with divorce papers from him, did not want to get blindsided again. I felt like I took an action on my own behalf rather than having the rug pulled out from under me.