Braxton Hicks or contractions?

Rose • 18 ~~ baby girl expected for 04/20 🧸🎀

Soo I just want to ask how do you know it’s Braxton Hicks and not actual contractions? How to recognize the actual deal.. I am 25 weeks and since 2 hours have bad period like cramping and a feeling of tightening as well as muscle cramps in my waist. And my belly gets very hard too. It stays for like 40 seconds then goes away then comes back 10 mins later.. should I be worried?