What does it mean when a guy says "I have intimacy issues..."?

I need advice on this boy. He told me he has intimacy issues, and needs his own space. Even though when we hang out we have a good time, and we see each other very regularly. (He contacts me.) But sometimes when I leave for a bit and plan to meet up later, he would call me and say “Actually I think I just wanna be by myself.” Usually this happens after I’ve seen him for a few days continuously. Recently when he came back from a business trip, he acted really sweet around me. But I just can’t get rid of the memory of him keeping me away as if I suffocate him. (Please understand I am the least clingy person I know…)