Is this a compliment or sumtin hurtful?

No one likes to hear their partner talk about an "ex". And it isn't sick that you live in the same complex; it just happened. It is hard for someone who doesn't know you and your boyfriend to understand what he meant by his message. You could ask him, but then you would have to hear more details about their relationship. It sounds like you are suspicious or hurt now so you will have to choose whether to ask him about it or to let it go and see how he acts in the future. "Actions speak louder than words."