Bizarre recurring temporary loss of interest

Alright, I was unsure of whether I should post this here or in the relationship subforum, so feel free to move the thread if this is the wrong place.

Anyways, I've been seeing a girl for a while now, although we are not serious, at least not yet. For once, this is actually an explicitly agreed upon thing. We had a little talk and decided that we are not going to take this too seriously, as both of us really still enjoy being single and are in no hurry to get into a relationship.

In any case, the problem I've been having is that I immediately after sex, I tend to lose interest in this woman. I just suddenly feel like I'd rather be hanging out by myself and I don't know, I just feel really odd after sex. I almost feel like I don't even like her in that moment.

Now, this would be a pretty simple case of me simply only wanting sex from this woman, but the thing is, it only happens immediately after sex. I like spending time with her just fine when I am not horny. So at least according to my logic, I must like her for reasons other than just sex, otherwise I would only want to hang out with her when I was after sex. Damn this is confusing.

Any experiences/opinions? This doesn't make any sense to me.

Thanks.

This is a tough situation in a society that values physical contact without any regard for emotional intimacy. Sometimes people even feel they have to have sex or they are not living by societal norms.

What if a person is really skittish about intimacy. It could be intimidating. It could be scary. It could cause someone to shutdown and shut off. Maybe stopping at touching and kissing and hugging is better for both people.

Here are some articles that discuss these ideas in more detail.
Psych Central - Search results for Intimacy versus sexuality

Actually, I wonder if it isn't a weird hormonal reaction. Men don't have much oxytocin in their systems, but right after orgasm, they experience a BIG rush of it. This is a hormone commonly thought to increase bonding in people (the "cuddle" hormone). Since you and this girl aren't serious and you know it, you might be having some weird reaction to the oxytocin rush? I dunno, the timing is what's making me think this.

How the 'Love Hormone' Works Its Magic ? WebMD