I Feel Like Im Going To Fail Socially

I moved to a new school last year. I have made many friends, but Im not close with them and I rarely hangout with them. Im scared to ask them to hangout. Im mates with some people that are well know and liked, some of them have tried getting me to join their friend group but I felt uncomfortable when I went to go check it out. I dont know some of the guys there so it feels awkward and I feel like an outsider. This is the friend group Id like to join, but I just dont know how. I also struggle to act like myself around new people. Its like I forget my own personality if that makes sense.

I also have a huge fear some of them wont/dont like me. These guys go to a lot of parties which I want in on.

My biggest fear is not living my teenage years to the fullest. So this is genuinely a big deal for me.

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Can someone give me advice on how to be more socially outgoing?