Hey mama, that stretching feeling is super normal at 4 months, your uterus is growing and pulling on the ligaments around it, kaya parang may slight tugging or stretching sensation talaga. A few of us felt the same thing and our OB said it's nothing to worry about, but since you're a first-timer and want peace of mind, I'd really suggest checking with your doctor just to be sure everything's on track, especially if it becomes painful or comes with spotting!