Changing Lock Issues

I’m an idiot. I know I’m an idiot. I thought I was in love. I was with a man for over a year and I trusted him enough with a key to my apartment. It was for late nights, like when he’d get home so late I didn’t want to leave my door unlocked or wake up to let him in so I figured that was the best option. I learned months later I wasn’t allowed to do that. He’d never be there when I wasn’t there so I figured it wouldn’t be an issue but he decided to break up with me by blocking me off of everything and not saying anything. I thought he was dead or in prison. I’ve tried asking for the key back, no response. I just want to get my locks changed and move on with my life but I can’t think of a reason other than the truth to give. I could get kicked out for this. It’s income based so the rules are a little strict. I can’t afford to live anywhere else and this stress on top of the heart break is becoming too much. I know I’m stupid, now I just need help.