perhaps, your dates are off. wait for two weeks more before getting PT
Hi,
by 8 weeks a baby and heartbeat should be showing. Is it possible that your dates are out?
If you are only 4 weeks instead of 8 weeks pregnant (and that spotting really was your period) then nothing would show yet on the u/s.
I would guess the next step would be either to have blood tests to check your levels and that they are rising appropriately, else repeat u/s in 2 weeks and see how things are looking by then.