The positive side to that is, it's fixable and very achievable if you wanna put your mind to it for real.
One of the best things you could have done was taken this girl on a date with 0 intentions. Go do something fun with her and treat her as you would a friend. Don't even consider kissing her. Take her out, make her smile and be done with it. This will help a lot I can guarantee it man.
Also, don't you have any friends who are super outgoing that you can stick around with to learn a couple tips from?
I have a childhood friend like that, and growing up he taught me ALOT about not giving a sh*t what people think. Not on a simplistic level but in the sense of just being yourself and acting naturally. Sometimes i even feel like some of the sh*t I say reminds me of him. This dude is literally just indifferent to everything around him lol. I actually admire the way he can be in a relationship, no jealousy, no back of the mind thoughts, still flirts but knows where to draw the line with other women.
I personally find relationships exhausting, I literally broke up with my last girl because she wanted to see me more than 2x a week and I wasn't feeling it like that. I hope this is jusy due to personal problems because I remember before hairloss, relationships were a lot more enjoyable for me.