Sometimes it doesn't mean that he doesn't want to have sex right away, it's always good to bring it up with each other, like find out if you guys have any std's or when you both are ready to go that far with each other. The other part might be that he doesn't want a relationship and just wants the sex part, but try to ask him what he means by talking about sex first.
If you mean he brought it up, as in, he wants to have sex with you, then tell him how you feel about it. If you're ready, make sure you're safe and are sure you really want to do it. If you aren't ready, then just simply tell him that. Do not force yourself to go through with anything you don't want to.
If you are not ready, then speak up and say so. You've only been together for a month, so it is kind of soon to be talking about sex. If he cares about you, then he will understand if you are not ready. More importantly, he won't push the issue.
You broke up with him for a very good reason. He is a highly selfish person and you are better off without him, in spite of how strongly you feel for him. Under no circumstances should you let him sweet-talk you back into dating him again.