Anyone else have anything similar happen?

I went in for my first ultrasound at what I thought would of been 6 weeks but the Dr I saw said in earlier than when I thought and I was closer to 5 weeks, he then wanted to see me a week later which would of been today and I went in and got another and it was bigger but he still couldn't find the heartbeat. He then proceeded to tell me l'm probably 5 1/2 weeks but he doesn’t know and he wants me to go back Friday and if he can't find the heartbeat at 6 weeks then I'm gonna miscarry. He said it with O emotion or consideration, I've read sometimes you can't find the heartbeat til & weeks so why would he even say that to me.. should I find a new doctor? Now I'm terrified and left In tears.