How do you know the difference between a strong Braxton Hicks and a real contraction?

These are the main differences :) Braxton Hicks are usually much more painful & last for a few minutes. They do not reoccur at regular intervals and are pretty harmless and normal. A contraction however gradually gets stronger over time, and comes in regular intervals. The time between the 2 intervals also gets closer and closer. It helps if you have your husband or someone with you to time the contractions so that you'll know if it's Braxton Hicks or the real deal :)