Next time he asks to see you, suggest you do something else. Don't go over to his or let him come over to yours late at night (say it's not a good time, have to get up early whatever). Let's say he asks to see you tomorrow, ask him what he wants to do, and suggest a movie you want to see or to go for a meal. If he doesn't want to do any of this, he is not worth the time. If he actually takes you out somewhere, continue in this manner and get to know each other a bit better. Go for dinner, have a drink (tipsy is clue, not drunk), find out more about him. When you feel like you're actually "dating", and you're comfortable enough around him to talk honestly, you can do the entire "where do you see this going".
Thing is, so many girls say they "don't necessarily want a relationship", but then they want respect, they want to know 'where they stand' and they want to have a label. There are only so many 'arrangements' possible. Unless you are basic **** buddies or actually a couple, there will always be a grey area. If you're not together but sleeping together, you will continue to wonder whether he is seeing someone else, whether you can, how strong his feelings are etc. Some people settle for that uncertainty, but it seems you want to clear things up, otherwise you wouldn't have written the post. Very few people are comfortable seeing someone over a long time with no definitions whatsoever.