The thing you overheard about you being flat on the front as well as your back could be a complement about you having a flat belly? That's how I would understand it with no context, at least.

I dunno, the whole bulge thing sounds very strange, I mean... who looks for that?! Nobody I've heard of, at least.

To me it's a jeans thing - sometimes they form bulge, sometimes they don't. Girls can't tell your size through the pants, and they won't try to, who cares about your dick size though, really? Do you care how tight a girl's pussy is? I don't think anybody cares, at all. And all teenage boys play with their junk in stupid ways, don't blame yourself or think you damaged it.

Bottom line is: You absolutely 100% sound like it's all in your head. Work on your personality and cunnilingus, my man, and realize this obsession or focal point of your insecurity is 100% in your head alone. You'll be fine then, lady-wise!