Well. I don’t even know where to start off. Short story i was raised by my mom my entire life, i knew i had a dad and he visited me almost every weekend when i was a kid, since a very young age i knew i had 3 sisters from his side but i never got to meet them until i was 17. 
I basically risked myself and contacted them, they didn't know about my existence and i think my dad had to tell them the truth. 
We have a good relationship but ofc i haven't met their mother or any relative from their mom’s family and i'm never invited to any celebration like NYE, birthday’s or any other event (which for me is fine, cause i respect their mom and space). 
I sometimes blame myself for all this mess my parents got into and i feel like i shouldn't be here at all I’ve recently felt awkward around them cause i feel like an outsider and nowadays i just want to be alone. 
Also i feel like i was a terrible idea because I technically broke a home even though my dad didn't live with them ik things got messy. 
Recently one of my sisters told me: "thank you for talk to us, you came to change our lives in a good way, sometimes you have a perspective about your dad and the news change that perspective" and even though ik she's happy i'm with them i felt terrible
 I've been to therapy and i went through it and i feel better with myself till now. 
My sister is getting married this coming weekend and i was pretty excited, but i got a call from my dad telling me to be ready cause their mom will be there, their relatives and friends as well and he talked to one of my sisters and said that it was fine, everything should flow as normal. But i don't feel like it, and now i feel like everyone will be looking at me and it’ll be awkward, so now i just don't want to go to the wedding but i feel terrible for skipping it. 
Wedding is close and basically i can't get a psychologist appointment before it and i don't have anyone to talk to so i'm sharing it here. Thanks