BH is normal even in the 2nd trimester but shouldn't feel too painful. Your body is preparing for labour. Comes at a few seconds and normally will go away when you move or change position ie. from sitting to lying down.
While contractions is painful. Like pressure kind of pain from your back to the tummy and heavy pressure at your pelvic. Does not go away when you move or change position. Differentiate the pain. If you feel this, time your contractions and head to the hospital if it comes every 5-10 mins. Don't need to wait until 2 mins to get out of the house. You might not make it to the hospital but labour midway there instead.