if you completed your period with the first guy then it is prob the new guy that is the father.
And it. Doesn't matter who the father is for u to be with them its who treats u better and who u love more
If u had a period after u slept with ur ex and only slept with the new friend after ur period it is more then likely the new friends baby. When you have a period it generally means you are not pregnant and the due goes by the first day of ur last period