Don't buy into your insecurities when you find yourself interested in someone. YOU may be insecure about your height, and you may THINK women don't notice you... but, that's only your opinion. It's in your mind. It doesn't mean the woman, or other people, see you that way at all. Whenever you start to feel those insecurities rise up, do something to counter-act them. Use it as an impetus to talk to a woman sometime. Or smile at a woman as you walk by, say hello.
What you project outwardly can help change what you think inwardly. We are what we think.