What Causes Morning Sickness, Sore Breast And Missed Periods After Miscarriage?

I was 6 weeks preg when miscarried on Jan 8th. It started with bright red blood then stopped- the next day I had a gush of blood with tissue. heavy bleeding for the next day then the bleeding stopped on the 4th day. I have had morning sickness, sore breast, ever since. my period was due 2/5 but nothing. is it possible that I did not expel everything and are having complications or am I having an imagined pregnancy?