Generally speaking, when someone is obsessing about their ex, that preoccupation causes the person to neglect themselves.

Are you eating healthily?

Are you drinking enough water?

Are you exercising?

Are you spending time with other people, family and friends?

Are you getting out of the house enough?

Are you avoiding drugs and alcohol?

Are you doing fun stuff, just for enjoyment?

Are you keeping up with your responsibilities?

Those are the things you need to do before you do anything else.