Exact same thing happened to me on Friday. I had the mammogram on Thursday and the radiologist called me Friday to come back in. I was freaking out. So I went in and the did the mammogram again and then the ultrasound. Everything was fine. They are just being careful. I totally undertsand you being worried. I was so worried. A million things went through my head.
I did have about 2 hours before the appt. so I went shopping. I am broke so I could only get a few things ,but it took my mind of waiting.
Hang in there. Don't let anyone tell you it is all in your head. You have a right to be worried. It is your body. I have faith you will be ok though.
On top of all that I had a bad Pap come back too. Just yesterday I had to have a biospy done. Double whammy. So far everything seems to be ok.
Thinking of you.