Why am I still insecure after all I've achieved?

I've been lifting for a year now and got huge but also fat. I've never really got attention from girls since my freshman year in high school. Well a few months ago started cutting weight and have attained a killer physique (not to brag). I get compliments all the time and girls are seriously paying waay more attention to me, and although my confidence feels like it's through the roof, I still can't muster the strength to make a move, even if a girl is clearly into me. It's as if I'm in the same boat as before.. It's been like 6 years now since I've had the confidence to flirt with any girl I like and I totally am a different person mentally now. I feel like I've been scarred when it comes to being able to flirt with girls and I'm in the best shape of my life! its killing me..
Why am I still insecure after all I've achieved?
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