I don't do this. But I can offer ideas as to what I think might help you. But first of all, I want to say that I commend you on your honesty here about this and your recognizing that you need to change it. Do the friends you lied/lie to really like you for who you are? Hard to say if part of their image of you is false, no matter how insignificant it may seem. Likely they'd like you and still be friends with you for you but you gotta come clean with that. The rewarded real friendships will be worth it.

Find one or more of your friends that you've been closest to, one you trust the most and start with them first. Start small and begin revealing the truth about yourself. If it's a person you trust, most likely they are the ones that will be the most accepting of your weaknesses. As you learn that one or two people that still are accepting of you, I imagine your motivation and courage to be more honest with others will grow stronger. I think the key, I must emphasize is finding that one person that you're close enough to that you can tell anything to and start with them.

You can do this. I have faith in you. *hugs*