I never felt this with my other pregnancys.
It could be that your placenta is low abd your uterus is stretching. Im 18w+5 wuth my 4th and have been having the same contractions. I went to the hospital and they said it could be the beginning of placenta previa due to each pregnancy attaches to diff spot mine is low
Are they braxton hicks? Have you experienced them with your other pregnancies?