Hi! I believe I can be of help with this issue.
First, let me say I can imagine how frustrating and confusing this situation must be for you. Being outgoing, social, quick, the life of the party, etc. are clearly not your strengths. Your friends seem to be kind and good friends but they seem as though they want you to expand your circle of friends and practice more being comfortable socially. That's how I understand the not inviting you to certain things. This is clearly tough for you. But they are right. You do need this practice.
To just up and turn your back on your friends is not the mature way. It is not the way of acting that will help you in becoming even more an adult. As adults we accept the lessons our friends are helping with us and we try to work on ourselves and get to where we need to be.
So, we need to work on your confidence. Confidence is something that comes with experience, like the experience of being whole and at peace with oneself and relaxed. But there's an impossible situation here: how can you have something that comes with experience before you've had experience? Well, you can't. You have to have what is "pre-confidence". What is pre-confidence? The motivation to overcome your nervous jitters and lack of confidence, lack of experience. Motivation is what gets you to get started before you have experience and so before you have confidence. Therefore, I want you to start reading motivational books. You need to see if you can let yourself be inspired by them. These are the best out there! If you can, great. It is not a magic cure, though. It is a way for you to change your mindset from "I am really sad and unworthy and lonely" to "I want to move forward and become the confident person I can be"...
So here are some books to look at as you continue in becoming an adult. They are not revolutionary, they are classics that each have something worthwhile for you to consider and to add to your questions and answers in life.
I think very highly of the first book on my list, which is a real classic: The Seven Habits of Highly Effective People by Stephen Covey. It is assertiveness thinking, but it is adult thinking all the way and is the book that has helped more people than probably any other.
The second book is by Anthony Robbins. He's one of those speakers who fills up huge auditoriums. For a reason. He's a terrific speaker and writer. The particular book (if you like it, try his others): Awaken the Giant Within.
The last book is the father of all these type of books. How to Win Friends and Influence People by Dale Carnegie. There are classes in these books now! It was written in the 1930s and still has something to say to you who lives on texting!
You can find all of these books easily on the internet with little investment. These books may or may not answer any specific question for you, but they will help direct you toward a way of looking at yourself in the world as an adult and as a man.
Okay. So you see I am trying to show you a way that doesn't just turn your back on your best friends but accepts maturely that you have some confidence building to do. I wish you the very best in this!
Please remember to click the green accept button. Feel free to continue the discussion; my goal is to get you the best answers possible. Bonuses are always appreciated! If I can be of further help with any issue, just put "for Dr. Mark" in the front of your new question, and I'll be the one to answer it. All the best, XXXXX XXXXX