It's the most insane thing I've ever been a part of. Around two months ago I began dating a new girl. We were together around a month and a half and she decided to dump me. She couldn't handle that I still partied with friends instead of being attached at the hip to her. The next day a friend of almost 6 years tells me she got jealous seeing me with her and she had a crush on me. I'm cool with that, so we start talking. Two days ago a girl at the bar I frequent and talk to all the time tells me she has feelings for me as well.

I'm tempted to start saying I'm in a relationship even if I'm not. What on earth makes women act like this?

Pre-selection in action

What makes things valuable? When lots of people want something in short supply.
If your in a relatonship that means other people want you (your girlfriend) and because you have a GF you are also in short supply (there is only 1 of you and someone already has it).