Possible preterm labor, any guidance welcome

So yesterday night I didn’t feel my baby move as much as normal. And I saw a small amount of blood when I wiped. Since I’m a FTM I panicked and went to the OB triage center of my hospital. They checked me and didn’t find any blood new or old and my son started up moving again. So I thought we’d be sent home. Nope turns out I’ve been having contractions and didn’t realize it (I’m only 31 weeks). They monitored me for 4 hours and I had consistent contractions 2-3 minutes apart the entire time. Since I wasn’t dilated they sent me home. We established I wasn’t dehydrated and I didn’t do anything to start them. They told me to watch out for preterm labor and have my OB monitor me and check me. Has anyone been through this?