Sore breasts after miscarriage?

I found out on March 2nd that I was pregnant, on March 12th I was having some heavy spotting and cramps and went to the hospital and was told I had a complete miscarriage even though my miscarriage had barely started. They gave me a RhoGam shot and sent me home where I passed jelly like blood and very thin uterine lining. By the next day all my pregnancy symptoms were gone. Now it’s been over two weeks since my miscarriage and starting yesterday my breasts have been really tender and yesterday I was having that stretching uterus feeling. Absolutely no symptoms of pregnancy between my miscarriage two weeks ago and the symptoms that started yesterday. Does anybody know why I might be having these symptoms that went away for two weeks and are now back? My bleeding stopped only a week ago so it would be weird for me to have my period this soon right? I know I must sound stupid but this is my first pregnancy/miscarriage and I’m a little worried they misdiagnosed me. They did an abdominal and vaginal ultrasound and said they didn’t see anything but I was only like 4 weeks along and had barely even started bleeding at that point so I feel like the baby would’ve still been in there. they entered my last period date wrong too and said my last period was on January 17th when it was January 27th.

So I guess my questions are:

Is it possible they just got my menstrual period dates wrong and couldn’t see anything because they put that I was 10 days further than I actually was?

And why did my symptoms stop for two weeks and then come back?