Nearly 30 with no real friends

For a long time now I have found so much peace of mind and comfort in being alone in my own space, doing whatever I want, just turning my brain off and shutting the world out (usually at nighttime). But on recent self-reflection I realised I don't have any close friends and I have isolated myself way too much over the years. I only have my partner and my family, and even then I don't really talk to my family about my personal life, and my partner can be rather blunt. I see my childhood friends every few months but we're not really as close as we used to be. I feel I have always struggled with social anxiety and I've been very shy and awkward in general ever since I was a kid. The only close friends I've ever had were extroverts that just took me in and I became part of the friend group by default. I don't talk to them anymore either, I just drifted apart from them.

Now I'm in my adult life, nearly 30 and it's terrifying how I have very little genuine connections with anybody. I have been described by my partner as unapproachable and sometimes come off as rude with other people even though it's not my intention. There are some acquaintances (mostly my partner's friends) who I really like and wish I was close friends with, but I'm just way too shy and scared to even start a conversation. I also feel like no one really cares about me, these people probably don't like me, if I died it would have no effect on anyone.

Yes, you might say it's my mindset holding me back but I've always had this never ending crippling fear of starting to connect with someone. I will always say something weird or whatever makes the conversation awkward. I don't know how to get rid of this fear, but now feels like the time to start as it has crippled most of my life quite a bit. Any ideas on how to start small and gain some confidence in making some friends? Even better, how do I stop being so shy and awkward altogether?