He may not realize that you are feeling a bit smothered.
Have you thought about talking to your ex boyfriend about your feelings? He may not realize that you are feeling a bit smothered. We all get over a breakup in a different way. He may not even realize that his presence is is troubling to you. I am sure that he would understand if you just talked to him. You cannot make him stay locked in his apartment but at least you will get thins off your chest. Do you think he would be willing to sit down with you to talk things over? It is always worth a try!