Staying overnight in hospital due to bleeding at 36 weeks..

This morning I started having red bleeding like a period with clots. I'm having regular tightening to my stomach and very mild period like cramps but nothing too painful. The doctors checked my cervix and said they need to keep me in overnight to monitor. She didn't mention if I was dilating or not. I'm still a little confused as to what could be happening. Has this happened to anyone else? Could I be having my baby early?