Dear Pete,  

There is simply no way to know for sure when you start. You figure, you trust, you ask for help, you do your part, you follow. The 'knowing' finally comes when the Church calls you and the Bishop lays his hands on you.  

Right now I think you need to visit a seminary, speak to the men there who are in charge of helping prospective candidates, tell them everything about yourself.  

You are already praying so stop waiting for the call to become clear, and go out to help it happen. God bless.