Our first sono and some questions for other mommas!

My husband and I were in tears seeing our second blessing brewing in my belly yesterday!! He or she is quiet the opposite of big brother. Baby was very still (big brother was so active) but had a strong heartbeat of 169 bpm! They told me I was 9 weeks and 5 days but when they saw the baby they said he or she was measuring two weeks behind so now I have a new due date of August 17th! I was a little disappointed knowing that I wasn’t as far a long as I thought I was! Has this happened to anyone else? Could the baby just be measuring small? Also I’ve gained three pounds so far and I’m only 8 weeks. Is that reason for concern? RAMZI THEORIES ARE APPERCIATED! 😁 Most of my family says girl! Thanks in advance of all of your answers to my questions!