zubi tried so hard na..she did so much to intice him and he was not moved,he never once corrected her when she said tum sadia se pyar karne lage ho(at dinner) during elevator he did say kya bakwaas kar rahi ho... .
she realized how much umair was getting jealous about ahmer and twisted the knife a bit.I agree he needed that baby was his and realized that everything else she said to him was correct.He also knew that sadia had never once said anything about ahmer.So now he was able to believe her without doubt and that was enough for him
He basically knew about his feelings but was not going to utter anything Bec he was insecure and yes he had lots of ego too..when be got the ring he was so happy, when he told his mom about baby girl he was so happy but the moment he saw ahmer laughing in car he was suspecting again..He called sadia to know and her line was busy..He was again jealous..why he never thought ahner could be talking to zubi but no sadia name came first. That's why I say he was always jealous of ahmer from the start.
Rem the scene on the phone when he said to zubi mujhe saaf saaf bato ka sadia ne ahmer ka baarien mein Kya kaha.he wanted to know everything. He even said he wants to know all what they discussed. Zubi even pointed out tumse bardashat nehi hoh raha na..