20 week ultrasound

So, i had my 20 week ultrasound 2 weeks ago exactly. It was done by a tech and not a dr so i know technically they arent supposed to say anything to you about issues they may see but when i was there i was getting a strange feeling because her facial expressions seemed off to me. My husband figured maybe she was just concentrating on the job at hand so i went with that. I decided things must be fine. My dr had told me at my last appointment (before the ultrasound) if there were any issues with the ultrasound she would call but if not she would see me at my next check up. Well today out of nowhere my dr called and left me a voicemail saying she needed to discuss some things with me about the ultrasound and to call back. I called 4 minutes (yes, only 4 minutes) later and the phones were already shut off because it was "after hours". Now i have to wait until tomorrow to even try and call back. So here is my question... what issues if any have you ladies encountered during these appointments. The baby is kicking a lot so hes active. Saturday i spotted a little bit of brown stuff but not enough that i think would be an issue so im at a loss as to what it could be. Also, i know there isnt anything that will come from worrying until i hear what she has to say but i just want to know of things that COULD come up. Just so im informed :) thank you ladies!