
An experienced vet / U/S operator would be able to see conceptuses at 22 days, (from ovulation not neccesarily from mating) but it is earlier than the optimum time if scanning for pregnancy diagnosis.
The probe is not really an issue as long as the settings are correct and the correct depth of penetration is being used.
you can see a pyometra at any time, ie no relevance if she is 22 days post mating, if she has a pyometra it would be clearly seen as fluid in the uterus.