Is he still interested, even after sex?

I started dating a guy a few weeks ago, he waited a couple of months for me to come back from overseas and we always talked, he sent me messages almost every day…
I decided to sleep with him and we talked about it before, and don’t want it to just happen and thats it…
I don’t think we are really officially ‘togather’ but we are taking it slow I think… On the night I said if I did sleep with him I wasn’t sure if it meant the same to him as it did to me… He asked me what it meant for me, I said for me, it means i’m starting a new relationship and don’t want a one night stand, he asked me what does it mean if we were boyfriend and girlfriend (we both are scared of having a new relationship, don’t want things to end badly) I told him nothing would change, probably see eachother frequantly and we don’t need to rush things and take our time, though I think we were thinking and wanting the same things. Ever since he still txts me almost every night to say hey… we plan to meet up soon (i think…. we were suppose to meet last weekend but we both got sick, we both called eachother that day but missed eachothers calls lol) and we always frequantly chat over msn…
I’m just wondering if any one could give me more advice, am I already in a relationship with this guy and just taking it slow at the moment? and What does it mean if he wants you more than once in one night? is that a good sign?