Anatomy scan questions!!

So I’m 18+4 weeks and they had said that I was scheduled early for the anatomy scan and it should have been scheduled for 20 weeks. They said for us not to be concerned if we don’t see everything cause we will just be seen back in a few weeks to recheck. The ultrasound seemed to go fine, and the tech said she didn’t see anything concerning but we will need to come back to get more pictures. When we talked to the doctor afterwards she said that she looked good but I’m still early and will need us to come back for better pictures. She also told us that our baby girls heartbeat was a little irregular. The bpm was normal at 133 but the beat was a “little irregular.” They said not to worry because most of the time it will correct itself and there is not need to worry and they will recheck it at 22 weeks. Has anyone else had this?!?? I still worry even if they tell me not too!!