I think this is true because of hormones. Our bodies flood with feel-good hormones like seratonin and endorphins after sex, which make us feel really happy and thus very connected to our partner. It's completely a physical thing, and maybe women interpret these feelings differently than men, or maybe they are just stronger in women.

Do you truly feel that you think having sex with a guy will make him love you? Or do you just feel so connected to them after sex, that you have told yourself that to justify it. Regardless, having sex with a guy will not make him love you- and I am sure you know that. In fact, if you meet a guy that you really like (that you would consider having a relationship with), it is usually not wise to sleep with him the first time you meet him, because he may get the wrong idea about you (u sleep around).

Hope that answers some of ur Qs...