Advice/Opinions on contractions

So I came to labor and delivery tonight because I was having very frequent and painful contractions. They said I was dehydrated so they have given me two bags of fluids and that didn’t stop the contractions so they gave me a shot and medicine to stop them. They have slowed down some..and I inconsistently have a wave of several in a row. He said I’ll take the medicine every 6 hours to try to keep slowing the contractions down. What if they don’t slow down? My cervix is only a fingertip dilated and hasn’t changed the whole time I’ve been here (4 hours). I’m just confused as to why I’m having to stay overnight and why they are continuing to give me the medicine if the contractions aren’t dilating my cervix.