3 rd request..please help me..i feel alone!

hi,
my sister and I live together and do many things together, lately she has been very involved with a guy and goes out with em alot, and i started feeling lonely, and i dunno why eveytime she goes out with em i feel like i wanna cry and i also feel "disgusted", i tried to undersand what is triggering this feeling and i don't know why, may i tell u something also: i htink i feel so because she invites me to go ut with them, and when iactually go for it, i feel in her commets that iam not welcomed.for example..i don;t think u will enjoy and stuff like this...so i thought may be by inviting me she just wanted to be nice to me and not rally invite me and so i started making excuses for not going out..plz tell me and help me ..why do i feel digusted..what do u think is this? i feel like i want to be completley alone now, i don't want to be with her i feel like she is being a hypocrite,,and we had a very honest interaction..everytime she brings the guy into the discussion she tells me that there is nothing going on btween them and i wonder why does she tell me that( i mean it is her life)..as if she is is insecure about it...aaah i feel very bad..what is this?

This guy has taken your sister away from you and destroyed your unique relationship. Of course you feel bad. You need a boyfriend or other friends. Do not give up until you are happy again.