Contractions/ Braxton hicks ?

Hello beautiful mommies ! So my question today is what do contractions/ Braxton hicks feel like early on? This is my second pregnancy 3 years later but to be fair I didn’t feel any contractions the first pregnancy until I was about 4/5 cm. My first birth went well thankfully and pretty fast long story short I woke up one day and my mucus plug came out wasn’t having any cramps before during or after maybe 2/3 hours later my water broke still couldn’t feel cramps/ contractions but they were showing while I was hooked up to the monitors at the hospital… so now this time around I’m having like dull lower back aches/ period cramps is this Braxton hicks? I’m 31 weeks