How to tell if these are braxton hicks contractions, or could it be signs of pre-term labor?

Labor. Braxton Hicks are defined as painless tighening and usually are also shorter than labor contractions. Preterm labor is typically painful and gets progressively worse. However, only way to know for sure if see your OB for an evaluation and possible uterine monitoring. A fetal fibronectin test may also help.