Hello girls, could you please tell me?

Hello girls, could you please tell me ?? how to understand that I have training contractions? Because I can't figure out the sensations - I ask the doctor, but she just says it's normal. In the evenings, I feel like my stomach is hardening, as if my uterus is coming into tone, and at night, sometimes for a minute my stomach starts pulling like during menstruation and then releases immediately.