Ok, I'd really like to help but I don't know you and don't have much info. But I've been quite in a similar situation a few years ago and I've come across quite a few shy persons, so here are my two cents based on a few asumptions I'm going to make.
So basically you have to deal with two problems :
1) You're doing something wrong that prevents you from being included in social groups
2) You're shy - afraid of people
IMHO, shyness in itself doesn't necessarily prevent you from having friends and meeting people. You can be shy, not talk much, and still be cheerful inside, something people will feel when they're around you. However, what shyness may cause is negative behaviours that make you look distant, standoffish or arrogant, like starring away or having a serious face. Perhaps when you do dare to make some humour it also comes of as "wrong comment, wrong moment" and that doesn't help either. That's what happens when you feel scared.
I wouldn't work on shyness itself, but only on the behaviours. You "just" really have to relax, smile to the world and look at it in the eyes. Just focus on doing so and enjoying the present moment. I know we've said it before, but I
insist because many things will come in their right place once you're able to do that. You will also quicky see that displaying a certain behaviour does trigger the related emotions. For instance, if you smile, after some time you'll realize that you actually feel happier, instead of the other way around.
Just do it
Good luck.