They made you feel like 'nothing without them' because they needed a crutch, honey.
They were - and no doubt still are - deeply jealous and envious of you, most probably because they could see that you were able to walk unaided.
In time you may come to feel sorry for them, but there's absolutely no need for you to rush getting to that state of grace 
Unless we have a passion for extreme sports such as mountaineering, white water rafting etc, we can all experience problems leaving our comfort zones - faced with the prospect of a bungee jump, I freely admit that wild horses will have a problem dragging me out of mine.
Is there any reason why you should choose or want to leave yours? If you want to dip your toe in the waters of unknown seas 'feel the fear and do it anyway' in the comforting knowledge that you can retreat to safe shores anytime.
BTW the title of your post 'A bit silly but' is misleading as there's absolutely nothing silly or frivolous about your concerns.
To sound more assertive than you may feel you are, remove the words 'but' or 'sorry' from your vocabularly. It'll slow down your speech as you try to find alternative words and you'll find that people will be more inclined to listen to what you're saying if you're not always making excuses 'but' or apologising 'sorry' for being you and expressing your valid opinions.