Need advice

Started out just letting my bf have some fun but he went a little too hard and it hurt for a second but he slowed down and it was okay. When i rolled over he stopped because i started bleeding so we went to the er because it wasn't stopping and it was bright red. Babies heart beat sounds good and he's still kicking around but they are still a little worried about my placenta possibly tearing off the wall. I wasn't effaced or dialated so they let me go home but even though its slowed down its still bright and now there's little string like pieces.... Could it be my mucus plug? I'm only 21+3 right now and i know if he comes he'd have no chance 💔