Liking my boyfriend less after having sex for the first time?

I have been with my boyfriend for a little bit over half a year, and three days ago, we had sex for the first time (for me, it actually was the very first time). I didn't enjoy it and didn't really feel a thing (emotions-wise) and while I consciously know that it is all just likely due to my lack of experience and that it will get better (eventually), I somehow afterwards only find myself thinking about what I don't like about him (he is a very nice, smart guy who calls me everyday, says how much he loves me etc.), how I don't feel he really cares about me, my problems... Has anyone felt the same way? One always hears about how having sex makes a woman feel more attached and all that, but for me, it is just the opposite...
Do you know what might be going on and how can I get rid of that feeling? On top of that, I still think everyday about my previous 'boyfriend' (we broke up because he went abroad and we were together for only a very short time -- a week or so), with whom I cannot be and know very little about... This is all plain crazy, please help me with an advice as to how I can change my thoughts. I don't know what to do.

Sometimes the actual event is a letdown from the anticipation and idea of it. I think far more often than not it's a great experience, and brings people closer together, but once in awhile the opposite can occur. Just see what happens, trust your gut.

It's never great the first time, and it probably won't be for quite a while. If your boyfriend is as inexperienced as you, it will take a while for him to build up some degree of skill, which is vital if you want to enjoy it.

The most effective way to enjoy it is to give him verbal feedback about what EXACTLY you like, and what you don't. Also, it would be helpful if you already understand your body enough to know what gives you orgasms, and give him directions.

I know it must sound very unromantic, but most men require at least SOME training.