Hello
As you are 25 days , late for period .
Doctor could not locate the sac or negative
pregnancy , while home pregnancy test is also NEGATIVE.
Doctor advised "DUPHASTON" i.e.
dydrogesterone 5 mg twice a day for 5 days .
Now about your question .
Is it a safe drug , if pregnancy .
Ans: Yes, this is a safe drug for fetus or mother , even if pregnancy.
Can't locate sac?
Yes, if doctor or staff is not trained , they may miss sac or can't locate .
So , once again get in
ultrasound and consult another gynecologist .
Because , you didn't mention , what do you want .
Answered your both question.
Good luck.