I think you should distance yourself from your mother for just a little bit. Stop calling her and when she calls keep the conversations brief. This is not to punish your mother, this is to give you some space to think about it. The fact that talking to her destroyed your day means that you cannot handle her right now. Too much is too much. She is going to be fine without you.

The thing you call Relationship OCD is something I can relate to a little. I have a Job OCD so to speak - I keep having work conversations in my head. These thought are very harmful because they can bring you down even if nothing in your environment has changed. Try to occupy your mind with something else, something good.