I actually might be the most dense guy ever walking the earth...

Flaskback to a few weeks ago (Persons involved are in the mid 20s):

Was hanging out with a few friends at a house. A friend of my roommates girlfriend was also there. Some friends gave me hints that she likes me or whatever. During the evening she gave multiple pretty f... obvious hints that I could if I wanted to. Dunno where my head was that evening but only realised that during the next morning. Nice.

Heared from reliable sources that she was frustrated because apparently I blocked of all her attempts that evening. Nice. Didn't see or spoke to her since then.

So this weekend was a bigger party. She was also there. And again she was trying and this time I was more receptive. There was a moment where we were suddenly by ourselves (like in a small partition from the party) and she is like: "Want to make out?". So we kissed a bit but I stopped here relatively quickly. Pretty sure I wanted to say something like: "Not here" or whatever. But I guess it came out a bit differently and the moment was gone. Nice. Party went on and we still had some interactions with each other. Evening was getting late and she decided to head home. Friend urged me to go with her but so did another girl. Nothing happened on the way home. Nice. Next morning I am just sitting there again and feel like the biggest retard in the world. Thinking about all the 100 things I could have done differently that evening and wondering why I didn't.

I don't even know whats going on. I basically have a good opportunity presented on a silver platter and still manage to somehow screw it up? I am just a total pussy. Afraid to do anything where I might get into an uncomfortable position. How do I find my balls to do what I want to do?