i used to be the exact same way when i was younger i was enveyous of one of my friends and i felt she had everything i didnt she was easy to talk to and pretty and etc etc and when i hung with a group of friends i always felt the odd one out i still have problems speaking in public plases and with new people but im not as shy as i used to be.
one day i thought to myself "theres no reason for me to be like this' every one is different and there are things about me that no one else has and everytime i feel shy or jelous i tell myself im perfect the way i am and theres no reason for me to be shy cause i should be me and if they don't lke me it was not meant to be either friend wise or significant other wise.
i hope i helped you out some :3