How long are the gaps between your U/S’s?

Sh

I had one at 7 weeks and then again at 9 weeks but my doctor had me schedule the next appointment at 15 weeks. I’m really nervous to be waiting that long.

Anything I can do to ease my nerves during this time? I’m currently 11 weeks and 3 days, was thinking about buying a Doppler but I know that it will just make me more paranoid if I can’t find the heart beat