This is a GP, not a gynaecologist. Do GPs ever use ultrasound? In any event, she did not use it,so there is no way she can tell for sure if the patient is pregnant.
No but their experience can. Im pretty sure the doctor didnt say it like that but probably said something on the lines of "you probably pregnant or have fibroids" '
You dont need a blood test to establish pregnancy after a certain time period the body changes quite distinctly (generally - however you definately need a blood test to RULE IT OUT). As for the confidentiality its not necessary if the patient agrees. Also there are times when it may be breached to provide better care for the patient in event of language or cultural barriers (however this is an extremely rare exception).
I honestly see nothing wrong with the manner the doctor carried it out. Are you sure those were the EXACT words the Dr used? if so then the Dr could use better manners and be a little more sincere but thats about it.
Also what if she required a referal to a specialist ? and the Dr wanted to inform you and be like "hey I cant treat this it requires an ultrasound" that is not breaching confidentiality at all
Edit:
from what you explained thus far and what the Dr has said means there is unknown vaginal bleeding of some sort. Which means its 5 possible diagnosis:
1) Pregnancy, attaching causing bleeding sometimes
2) Fibroids
3) Endometriosis
4) A vaginal infection
5) Laceration from sexual intercourse
To the lay person these things may seem taboo to talk about so openly but to a medical professional its normal. They may not be a gynaecologist but they have worked as gynae units and are trained in it. The ultrasound is done to confirm which of the possible diagnosis it is and to show cysts if any.
Most likely one would need to use a contraceptive pill and tranexemic acid to stop the bleeding if any. If the situation worsens then one will need to look into more complex and extreme diagnosis