He means basically what he is saying, that right now he is not interested in a relationship. He is happy where he is in life, and does not want anything to change it. What he is telling you is he had a good time with you, and that while he does like you he wants to take things slow. Basically instead of looking at this as a soon to be relationship, just take it as it goes and see what happens. He is telling you that he does not want to be in a relationship, but he is not opposed to seeing you again and if something happens then great, if not then so be it.
Right now the ball is in his court, you need to wait it out and see if he contacts you again. Give it a week or two and if you hear nothing back send him a text asking him if he wants to go out sometime for dinner or something.
What I can tell you is make sure this does not become a situation where he calls and you come running for sexual activities. While I am not saying he is one of those guys, the reality is he has plainly told you he isn't interested in a relationship and since you did hook up the last time he could have it in his head that hooking up is good enough for you. It sounds like this is not what you are looking for so make sure you keep your eyes open and make sure this is not what it turns into.
If he wants to get together again make sure it is a date, if things become intimate again that is fine if that is what you want. Just make sure it does not fall into something that you are not looking for.