Ay, normal lang yan usually sa 16 weeks kaya don't worry too much! I had the same thing with my first, parang mild cramps or stretching feeling lang, and my OB said it's just your ligaments stretching as baby grows, pero mas safe pa rin na i-mention mo sa next check-up mo para fully reassured ka, lalo na if it gets stronger or may spotting na kasama. A few of us moms get this feeling especially around mid-pregnancy, parang tumatagal sya for a few weeks then naiiwan na, pero every pregnancy is different kaya best talaga na i-confirm with your doctor para sa peace of mind mo!