Curious about dilating

Hi! I'm a STM. With my first I was induced and had meds at 2 cm at 41 weeks! Well this pregnancy I'm 31 weeks 1 day. I've been feeling Braxton Hicks often! The BHs are getting more intensed and I actually have shortness of breath with them. Well lately I've been walking and feeling pulling each time. I pass it as my body is stretching. For all the STM or +, how do you know when you're dilating? My doctor told me if I feel the BHs every 5 minutes that's when I need to go