What must be done now; should I fast and offer expiation for all the days I missed before and after pregnancy, or fast without expiation?

The bleeding after a miscarriage at two weeks of pregnancy is not considered post-natal bleeding (nifas); rather, it is irregular bleeding (istihada), unless it coincides with the time of menstruation, in which case it is considered menstruation.

You were obliged to fast during the time of istihada and to break your fast during the days of menstruation.

If you broke your fast for the entire period due to ignorance of the ruling, there is no sin upon you if you did not neglect to inquire; otherwise, repent to Allah.

You must make up only the days you missed fasting, without expiation.

As for the two days you broke your fast during pregnancy, you must make them up. If the reason for breaking the fast was fear for the fetus, then its guardian must feed two poor persons for each day.