How to deal with social anxiety?

I've always been anxious and shy and withdrawn. People have always commented on that too through my life, like being a quiet person make them uncomfortable. I feel like it gets worse the older I get. I feel like people don't like me cause I'm shy and not loud and talkative and not interesting or good looking enough.

My fiancé says I'm overreacting but it doesn't feel like that to me.

The problem is that I would love to be social and make friends (I have none) but as soon as I find myself in a social situation with people I don't know what to do. I withdraw and try not to make eye contact with people. I feel like it's easier for me to make friends with males cause I have bad experience from women/girls as friends. My fiancé says I need to be more friendly which makes me feel like I should just stop trying.

It's particularly hard cause I'm a musician so making connections and such is extremely important. I just feel like I've lost the last bit of confidence I thought I had and I'm 27. I feel like a real failure because of this.

How do you deal with social anxiety?