so now yash will become sherlock holmes. i bet he will find her behaviour to be suspicious. if she has to go to the hospital to pick up her meds, she will try to leave the house saying she has to run some errands.
yash will try to drive her but she will say no and he will be adament but she will still say no. here i feel he would follow her to the hospital and finds her in the hospital just as she is leaving. she can get all pissed and be like why are you here! and then as he is trying to respond the doctor can come running behind and say "Ms. Scindia you forgot your meds! Make sure you take these because it is very important for your baby!"
here she could try to run away from yash but he won't have it and he will confront her and be like why didn't u tell me and she could be like because u said that night was a sin and therefore you will consider this child to be a sin as well.
we see he is already feeling confused, this will make him sad and confused because he can now see how his behaviour has affected aarti.
yash will find out before G3 comes back. remember she said that when she returns, she expects to see aarti, yash and their kids their to greet her and that aarti will bring happiness to the family...that was totally alluding to the news of her being pregnant.