What happened?!?!?!

June 30th I started bleeding but it was very light and faint but as the day went on it got a little stronger and pinker so I called the Dr she said to go ahead and go in and they would check if anything was wrong... My ultrasound measured 7 weeks 1 day and a strong heartbeat of 139bpm.. She put me on bed rest and sent me on my way.. I got home and took a nap when I woke up I went to use the RR and there was blood a lot of it and clots.. I went to the er and they confirmed I had misscarried... I don't understand... How could everything be so right n around 4 hours later be so wrong!! 😭😭 I'm devestated!! My second mc a year apart!