Braxton hicks should not feel painful at all. It's just a very uncomfortable, tightening feeling. Normally comes and goes. My guess is you're having a contraction. Pls do time your pain interval. If it gets too intense and very frequent like every 5-10 mins then it's better to head down to the hospital. Not every pregnancies ends with a burst of the waterbag or bloody show. Most, only with contractions. You may want to call the hospital first and let them know that you're feeling pain so they can prepare for your arrival.
Seems very similar to what I experienced last week before I went into labour. In my case, The mild contractions started off very sporadically for around 24 hours, in the subsequent 24 hours they become more regular and stronger but still manageable pain wise ie 15-20 mins interval. Contractions become more regular the following 12 hours or so ie every 5-10 mins once lasting about 10-20 seconds. I was 2cm dilated when checked into hospital.