Nerves.......😰

To
This is my first pregnancy. After realizing I haven't had my period since December me and my husband took our pregnancy test in February and in fact we are pregnant. Well according to my last period date and my first Doctors appointment which was March 3rd, my dates were off. From December to March I would've read 11wks but my doctor told me I was 9wks. That put me back 17 days. Why is strange because I hadn't had my period and I so lightly spotted for half a day in January. We had a ultrasound and saw the baby and it seems healthy, no movement, but it was there and had a strong heartbeat. I'm just worried about the date being off and if my baby stopped growing. We heard and saw a heartbeat but the dates and its measurements threw me off. With First finding out I used to have consistent cramps and being told it was my uterus growing and feeling nauseated all the time. Since my appointment, they BOTH have completely STOPPED. This is our first baby and idk what to do. Idk how I should feel. I'm worried that I'm baby did stop growing because I don't cramp anymore I'm not sick anymore and the measurements were less than my last period date. I don't know what to expect since it's too early to feel any movement to know my baby is still there. My next appointment isn't until April. Should I be worried or is it just my nerves bothering me too much? This is our bean from his/her first appointment. The Umbilical cord and placenta sack looks great.
 *note_the 11wks2d at the top and the baby's size.