Yan ang Braxton Hicks contractions, mommy, practice contractions lang yan na normal sa second trimester, lalo na pag tumayo or gumagalaw ka bigla! Pero since you're 19 weeks pa lang at may tightening + pain, mas better na i-check mo pa rin with your OB para maging sure na lahat ay okay, especially kung paulit-ulit or nag-aalala ka na talaga.