Engine running badly and poor gas mileage

I drove my car to work yesterday and it drove as usual with no issue. As I was getting ready to leave work I started my car and it was jumpy like and almost flood sounding. The whole way home it would not accelerate correctly. The RPM went up to 5 and stayed at the same speed it barely accelerate. It has no go on the uphill it almost totally shuts off and it is eating gas like crazy. I was under it today and noticed flames coming out of the piping before my flex pipe. I am not sure where to start but could use help.