19 weeks 5 days .. Always worrying /:

Yesenia • Single Mother (33) of 3 .. My king (15), My princess (13) and My prince (expecting in April 2015)
I'm just a worry mami .. Ugh!! So last week (18 weeks 6 days) I had my full anatomy ultrasound & found out I'm having a boy (excited) .. The tech said everything look healthy including the baby but then she says the baby looks like he is 17 weeks instead of what I was at the moment so they were going to change my due date to April 17 .. Then another doctor came looked and said everything looked great and not to worry .. They scheduled me to come back in 4 weeks to check the baby's growth .. Even my midwife said not to worry that I'm a small person (5'2") and father as well (5'6"-5'7") .. Well I'm still worried .. I don't know how to ease my mind .. I feel everything is fine & I know he is fine but God since I got pregnant all I do is worry .. This is my third baby but kinda like my first since my other kids are 12 & 14 .. Sorry I just needed to vent & maybe I can feel a better & someone will understand my feelings since I really don't have anyone that can .. I love my baby boy & all I want is a full term healthy baby ..