@MDT
I understand how you feel as I tend to get quite anxious before going out socially too. But you might have a good time, so it's maybe worth going and trying to enjoy yourself? Maybe try not to focus on yourself but look at the other people you are with?
I worry about my appearance usually because I am quite depressed and unmotivated so to get dressed up and make an effort with my appearance is quite difficult for me. I'd rather just go in trackpants but then people make comments that I look like I just got out of bed. I don't know exactly what to say to make you feel better about yourself but maybe just try to remember that we all struggle with how we look. If we are overweight we want to be slimmer, if we are slimmer we want to be prettier. If we have curly hair we want straight hair. If we are blonde, we want to be brunette etc. etc. You said you are very tall? I am the opposite as I am quite small and people make rude comments, so I wear high heels a lot to make myself look taller, but they are uncomfortable to walk in.
I hope you can go tonight and try not to worry about what others think of you. They are probably all worried about themselves too. There are many people in the world with lots of physical problems (wheelchairs etc.) who find it difficult to go out anywhere. I think personality always outshines appearances and sometimes the most beautiful looking people turn out to not be the most interesting ones to talk to. Maybe go out with the intention of making a new friend and learning something new about someone?
Hope you have a good night out and can share something interesting with us tomorrow.