As the story is progressing everyone is witnessing Raghav's growing insecurities. This insecurity is making him do mistakes now and probably more often in future. Inspite of such strong promises made to one another , one would think why is Raghav insecure?
Raghav had a difficult time growing up. Pain has definitely been a part of both Raghav and Pallavi's life but Raghav has had a more difficult life than Pallavi. Whatever situation Pallavi has been in , she always had people who loved and cared for her . But has dealt wid people leaving him since very young age. First he had to witness the brutal lynching of his Appa and his younger brother for which he was blamed by everyone including he himself. Then he was left all alone to fyt his demons by his only living family.....his mom and Keerthi. Even now he has not completely earned the love his sister.
When he found Pallavi , he found companionship. In her he found someone who tried to see the Raghav underneath the Raghav Rao. He has never considered himself worthy of her. It so evident when he says word like she "accepted" him. Yes she did accepted him wid all his flaws. And she is the one wid whom he has shared his deepest fears and root of his insecurities . How many times has he asked and requested her to stay in his life, to not leave him alone.......even when they were not in love. He changed himself ......so that she would choose to be wid him. So better to understand his insecurities over losing his "one" to her ex.
Not saying he is ryt but his deep seated insecurities over people abandoning him combined with his knowledge of the ulterior motives of Mandar is making him act out.