Hi Ellana

At 4 weeks u/s wouldn't see bub...HcG levels are good for 4 weeks...
I get scanned early due to previous ruptured ectopic..but early for my clinic is 5.5 weeks and even then we're lucky to see a gest sac...HcG needs to double every couple of days until about 6 weeks so the next BT will give you a better idea of how things are going.

Good luck...I hope everything goes well xxx