i was harassed in my past and it still hurts me, please help me give some advice.?

[Brad 1989]

in my school life i was harassed by my friends and some of my teachers and due to some family problems i didn't get support from my family. with time i lost my confidence to speak to the strangers and making new friends and even i can't talk with my parents openly and with time my behavior changed to clingy and dependent one. with time i lost so many friends but i didn't understand my problem properly. but currently i lost my best friend due to my clingy and dependent behavior, she is like sister to me but i lost her due to my clingy and dependent behavior. she told me earlier to change my behavior but i failed. i have no confidence to speak with strangers and making new friends and maximum of my friendship never last long due to my clingy behavior. i know i irritate my friends with my clingy behavior thats why they all left me. but i don't want to lost more friends, i lost so many friends, my best friend due to my clingy behavior in my life now i don't want to lost more friends but i don't know how to change myself. now i have no true friend with whom i can share my problem. please give some advice i am feeling so lonely..