It's not that dating is easy for everyone else. It is just easier for your girlfriend than just about everyone else. Sounds like you are feeling rather hurt and perhaps you are feeling a need for your girlfriend to slow down a bit and allow you to catch up to where you want to me in your own dating world.
I feel the comment about not understanding why you aren't constantly surrounded by women to be rather condescending...as if if is some fault of your own that you aren't. In fact, your feeling intimidated over your girlfriends focus on her other relationships over your feelings sure isn't helping you be attractive to anyone else. Here again is more reason for her to slow down on her outside relationships if your happiness is truly important to her.
I want to be clear that I'm not saying that she has any direct power over your emotions. We cannot expect anyone else to be able to make us feel a certain way. However, I feel it is very important for primary partners to show they take their partner's emotions into consideration and choose to make sacrifices when their partner is feeling hurt by a situation that involves both of them.