Boyfriend distancing himself...?

My boyfriend and I have been together for a year and a half. The relationship was pretty rocky during the start but it has been very good lately. We have lived together since last July and things have been going well. We have an occasional fight now and then. Right now though, I am attending school and I have been gone for one month so far. I came back and my boyfriend was happy to see me but then I had to go away for a couple more days and when I came back I asked for a kiss. I missed him. He said he didn't like to kiss me in public...there really hasn't been a problem before. Then later on that night he said that he just needs some space. He didn't say anything about breaking up but he meant that I am suffocating him I guess. We haven't slept in the same bed for about a month and we don't have sex but rarely anymore. I don't understand how much more space he thinks he needs if I haven't really properly seen him in a month. My question is what is he trying to accomplish by distancing himself from me?...sorry so long.