What Causes Soreness In The Breast After An Abortion?

hi, i had a medical abortion 2 days ago, i was 4 weeks pregnant, and my breasts feel really sore today. i didnt have this feeling before and im worried the abortion didnt work as the clinic told me there is a 48% chance it will fail as it was performed at such an early stage. they only told me this in the afternoon 6 hours after i'd taken the tablet. if id known before i would have waited another couple of weeks before i had the termination. im so worried i may still be pregnant as my breasts weren't sore before.