I need advice!!!!

So I already go to the doctors 2x a week.. With more than 1 appt in those days. I am having non stress tests twice a week along with an ultrasound a week and a regular checkup a week. He is weighing in at almost 4 lbs I am 33 weeks tomorrow and he seems to be right on track ... But apparently my uterus isn't measuring as big as it should be?? So not I have to go to a midwife once a week to measure myself... The non stress tests are going perfect.. He is very active and on point for his weight. Just growing in the 20th% ... Should I be worried. This is my second son I never has issues like this with my other pregnancy. .. Helpppp!!!!