As someone already pointed out, you should NEVER allow the two to breed unattended. The female trying to separate from the male could result in serious injury for both of them.
No offense, but the questions you are asking are
very basic aspects of breeding that you should research and know the answers to waaaayyy BEFORE you start trying to breed. I have to wonder if you are having these issues now, what kind of issues are going to come up with your females pregnancy that you will not know how to handle that could put her life at risk?

Breeding
responsibly is something that takes LOTS of research FIRST. It is not a learn-as-you-go process. My honest suggestion would be to stop trying to breed them altogether for now and study up before you attempt it again.
You've come to the right place to get lots of good information and help, if you are willing to take the time to soak it all in and learn. Doing so will be a huge benefit to both you and your dogs.