If sex is just sex why act like this?

I have been dating this guy for a little bit. Chemistry was good and we ended up having sex the second date. He said sex is just sex and no emotional attachment. We are going to continue dating and see where it goes we both want something serious. Over the coming days he started to say he doesn't want me talking to other guys and that we should be exclusive to each other..

I started getting I miss you text, you're beautiful and I'm thinking of you. One time after sex he said I hope this showed I missed you baby.

So I assumed he caught feelings. We recently got into an argument and the sex stopped by him refusing to see me; even when I told him I just want sex. 2 weeks later we had the conversation to fix things and he admitted he thought we had a good thing going that would be leading to a relationship before our argument. I said let's take things slow and we will be back to where we were at. He said ok and now he wants to resume sex.

I don't understand why the sex stopped if we were having a disagreement unless he started to get emotional attached and sex isn't just sex anymore? What do you think does he have feelings and are strings beginning to be attached to sex?