Seeing the last few episodes I get the impression that Milind is trying to push Prachi away because he is ashamed - 1. for forcing her to marry him knowing that she was in love with Neev 2. about his background since his family had worked for Prachi's family.
Initially his vergence for Ayesha was all consuming. He married Prachi only to make a her feel jealous. And man did he succeed. Now Madam is literally seathing in jealousy. Alaap's disgrace of his family was also a convenient excuse to torture Prachi. He believed Ayesha's lies against Prachi and did not feel any remorse for his rough attitude. In this phase all he felt was anger, no shame.
When he realised that Prachi's care and concern for him was genuine, he was breifly ashamed of his behaviour (particularly his near rape). He allowed her the choice to stay or leave assuring her that he will fully understand if she does want to leave. The independence day celebrations was an eye opener to him. He realised he enjoyed her company and thought she too reciprocated. In this phase (if you can call it that for it was only for a very short time) he was genuinely happy. He felt he was making some head way in his marriage. Remember the scene where he rushes back home from work on the reunion party day thinking that at last he will get to spend time with his Prachi without the presence of Neev and Ayesha.
While the independence day party served to bring the two love birds close, the reunion party ironically tore them apart. Prachi's attendance of the party (despite her proclaimed disinterest for parties) and Neev's declaration of love were like slaps on his face. Her presence in the party seemed to underline the difference in their social status which till then had not bothered him. Neev's declaration showed him what he had inadvertantly snatched from them (Neev and Prachi). If it had not been for Ayesha and him those two would have gotten together. Prachi's claims to hold the institution of marriage above all else only made it worse. Since he thought that she is stuck with him even though her heart lies elsewhere. And he was responsible for this mess. So right now the duffer can only feel shame for his attitude. We saw that in yesterday's episode as well. When he was asking Prachi to stay back he could not meet her eyes. He felt guilty for again coming in the way of her happiness.