35 weeks and have been stuck at 1 1/2 cm for a few weeks so I over analyze all symptoms

A few hours ago I felt what I thought was a contraction. The pain was super intense. It only happened once so I didn’t think much of it. Then about half an hour ago, I felt like I had to vomit and have vomited twice since but have been nauseous the whole time. (I haven’t been sick this whole pregnancy). Now I feel super dehydrated and dizzy. Haven’t had any contractions but my belly feels heavy and I have minor back pressure.