Tantor

So I started seeing a girl recently (we're in our mid 20's) and we've really hit it off I feel, hardly an awkward moment and plenty of laughs and entertaining conversation for hours. After our first date came the awkward moment of the goodnight kiss. She made it very obvious that the invitation was open, so I moved in and we had a quick kiss after which she said "I'm awkward, bye" and pretty much ran to her car and drove off quickly.

Second date ended similarly with a longer more intimate kiss and her speeding off once again.

Third date was back to just a quick smooch and a speedy exit.

(Each date went well and we both said we had a good time right after as well as in texts later)

I'm fine with it for the most part (I'm in no rush and I like her a lot) but I'm kind of curious about the reason for her speedy retreat just to make sure I'm not doing anything wrong or if she's not that into me. She continues to go out with me so I would think she likes me but it sort of makes me wonder.

So do girls do this sort of thing often? and for what reason would she maybe make a break for it after having a good time?

Building self esteem seems to be a constant reply to people's questions regarding how to fix their lives and overcome personal issues and also in trying to find a relationship, but how does one actually build self esteem when they seemingly have nothing going for them (ie. no job, friends, significant other, negative self image)?