<human>: Not really sure where to start this, but I guess the only place to start is with a bit of backstory about me.

So, I'm 18, male, 6ft exact and have an athletic build.

I'm also unbelievably insecure when it comes to my personal image and how i look

Now, the problem is, all people ever tell me is how good looking I am. Without me asking if I'm attractive or not, I just get constant compliments, daily.
I've never ever had a problem picking up girls either.

But, I do have a problem approaching them, because when I look in the mirror, I don't see what people tell me they see. And because of that, I can never approach anyone.

99% of the time, people will approach me and even then I get all flustered and don't know what too say.

Keep in mind I'm not a virgin and have had a few long relationships.

For example, the other night I was out with friends, and two girls out the blue approached me and sat next to me.
They would not stop trying to get a conversation started, as I desperately tried to stop it from happening (out of nerves)
I eventually just got up and left to the bar

Quickly followed by a friend asking me why i walked off and blah blah, you understand the point by now I'm sure

So, I'm just after advice really, in my daily routine I'll get constant compliments from random people (I work in retail) and if I go out on a Friday night, on average 2-3 girls will try and approach me 

But I'm so insecure about how I look and feel so ugly that I struggle too start anything

I'm also not a shy person, it's just when I know there's a girl who's interested, it's more... Intimidating? Maybe, I'm not sure how to properly explain it.

I hope that makes sense to read, if not

Give me the gist of the text in a nutshell
<bot>: I'm not ugly and I know I'm not, but I'm massively insecure and can't approach girls at all, and if they approach me I melt inside.