I'm 5'8 and feel insecure about my height. My girlfriend is 5'6 and she towers over me in heels. This and being smaller than other guys, makes me feel less important. I tried working out and gaining mass, with success (abs, more muscle) but I still don't feel confident. I feel like I'm at a disadvantage everywhere including dating.
My girlfriend did say that I was short, and after I got offended apologized quickly and said.. "Your height isn't THAT bad..." I haven't spoken to her since.
Well if your height bothered her she wouldn't be with you to begin with. She's obviously attracted to you. I think you need more confidence because 5'8" is around average height. If you're secure and confident in yourself it shouldn't be a problem.