Heart beat too soon?

Levikingston • ❤️Levi Kingston Lam❤️
I ask this question because I'm kinda confused .... 
My lmp June 18. 
Took a pregnancy test around third week of July. Had some bleeding and went to the er at the end of July and have a ultrasound and I saw the heart beat.... And I'm thinking isn't that too soon? So can I get pregnant before my missed period?