Can you get sick from an early miscarriage?

Hi!
A question for the ladies who unfortunately had a miscarriage. I gave birth not too long ago, and went straight back on the pill (a lighter one than before, didn't get sick and didn't forget any pills). Early last week I didn't feel well, and was really tired. I took a test and it was positive. Quite a shock since I'm on the pill and gave birth not long ago. Two days after the positive test, I started bleeding, just like a normal period, with some cramps here and there. I tested again and it was much lighter then. So, miscarriage. But now, for the past 3 days, my breasts have been hurting/feeling fuller, I suddenly feel incredibly nauseous, and just feel crazy. Could this still be from the miscarriage? Are my hormones just all over the place? Is this still the after-effects of my previous pregnancy? Does anyone have any idea?
Love!