Someone in the forum used the word "trigger" and that really got me thinking.
I've read only the updates and yet to watch today's epi. While Rohit's behavior is not commendable, but, from a psychological pov, i kinda get where he is coming from.
I think more than being synonymous to love, Raima has become a sort of trigger which reminds Rohit of the past "trauma" which causes him an overwhelming amount of sadness, makes him lose tracks of his surroundings and in a way "relive" the trauma (that is, the failed operation), hence evoking feelings of guilt.
Remembering her birthday was a habit to him. The fact that he broke the pattern he has been following for years puts him in a situation of distress and that's where his defence mechanism comes in.
Denial. It is one of the many coping mechanisms "in which reality is avoided by defying the existence of the problem." I think unconsciously he realises that he feels for Sona, however, because of the strings that still binds him to Raima, he feels that whatever he is feeling is unacceptable. Denial is a way to protect oneself from feelings of shame (at not being loyal to Raima) and guilt.
The denial allows him to pretend that his equation with Sona is not real and has no impact on him. Denial also stops one from taking responsibility for their choices, leaving them free to continue to blame others. At this point, with no closure on his past, he is unable to accept his feelings and hence, is blaming sona for the same. This is a way of shunning her out.
He is blaming to shift the responsibility (of loving, of forgetting) which he thinks he has, as a way of showing loyalty to appease his guilt.
He is doing/will be doing everything to escape reality: repressing of feelings, denial, blame shifting and then, he will reach a point where he will have to be honest with himself.
Of course, of course, I know that the writers may not be thinking along these intricate lines, but that's just a reading of Rohit.