Ok so this is my two bits..
Om and Riddhima have been in a relationship for 3 years but have never been together at the same place for very long. It seems that She was constantly travelling for her documentary. Remember even Rudra right in the beginning said that he forgot Om had a girlfriend coz shes never around. So I think whenever they probably met they were just happy to be together and now that she has finally come back for good and the honeymoon period of the relationship is over the reality is striking.
Om is used to his space and doing things his way ... Ridhhima on the other hand wants to change things around in Om's space thinking that now that shes there she should do all this. Om being a passive character is not able to voice his opinions coz he doesnt want to hurt her.
These are small things but u can begin to see the cracks in their relationship. Om is starting to feel confined in Riddhima's presence and being an artist and a person with a creative mind he doesnt like that.
Eventually it will be a bigger reason that will make Om end the relationship and not just these silly things. They are just showing the relationship cracking.. the final break will take some time.