How many ultrasounds did you have throughout your pregnancy?

I just read that the doc normally only gives one or two ultrasounds during your pregnancy. Well I had one ultrasound at 6 weeks (to determine how far along I was), one at 12 weeks (I requested bc I wanted a pic). I had one at 17 weeks... they originally took me to a room without an ultrasound machine, then the nurse moved me to the room with one. Now I have a doctors appt at 20 weeks with my regular doc and the nurse scheduled a detailed ultrasound at 21 weeks with another doctor to determine if their are any problems and the sex of the baby. How many ultrasounds did you get during your pregnancy? If the doc even thinks something may be wrong, would she tell me or would she keep her concerns to herself until she knows for sure? I'm panicking!!
I haven't had bleeding... some slight cramping. She did say I was dehydrated last time (at 17 weeks).

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