hi i had the same pattern of braxton hicks at about 36 weeks with my last pregnancy. i ended up being 2 cm dilated at 36 weeks and 3cm at 38 weeks but was induced at 38 weeks 4 days for medical reasons. you may just want to check with your care provider just in case. mine were similiar ie regular pattern, woke me through the night, lasting for awhile.

im 31 weeks too with this third pregnancy. getting quite a lot of strong braxton hicks but nothing regular so i think you should check it out just to be on the safe side.

best wishes.

beccas