Braxton Hicks or Actual Contractions?

I’m almost 18 weeks and I’ve been having Braxton Hicks for weeks now. Today, I’ve been having them for a few hours now. They feel like period cramps kind of. This isn’t my first pregnancy but I didn’t really feel the Braxton Hicks until late in the pregnancy. It’s kinda worrying me. When do you know when something is wrong and go to the hospital?

*Update- I’m not dehydrated and Braxton Hicks start early. It’ll be hard to time them because the pain seems consistent...I’ll try though