How to make him wait a little bit?

I met someone 3 weeks ago, since then we met like 5 times. Everything goes slowly between us, maybe at the beginning he was a little bit shy, we kissed for the first time after the third date (and we're 28!), but during the 5th one I felt that he really wanted to stay the night;) I refused because I don't feel yet if he is attached enough to do that... He seemed to understand and agree, but we'll see how much time he will be able to wait...

The thing is that I don't know how to be sure if this is serious or not. I don't want to be just a one-month girlfriend, I want a real relationship. He seems serious, too, he waited with the gestures and everything, but now, knowing that we both feel sth, the question of sex is inevitable... I have nth against it, but I would like to keep this guy, and I'm not 100% sure if he will still call me after that and stay with me - because still, we don't know each other well.. Sex is important for me, it means something, so I don't want to do it for fun.

So - how to play it well..? If now he doesn't come back, that's clear. But if we stay in touch, how to make him wait for our first night together and not exaggerate? And how to know the good moment - I mean, how will I know that he is attached enough to stay with me...?

For the moment it's all rather cool, for example I know that he is really into his friends, he spends a lot of time with them, for the moment they are more important than me, but that's ok, he knows them for years. But if it doesn't change, if he will still choose his friends over me - will it mean that he's looking just for the sex, or it can be just the way of living?