Is it over for me?

I don't have enough information to conclude that. What I can tell you instead, is that
virtually every man confronts this problem (more than once) in life. I can also say that some guys fail at confronting and overcoming these feelings and some even end up being confused about their identity and sexuality and remain unhappy.

What we know for now is that you don't lack social skills, since these are not selective, you encounter an extremely common problem and that failing to overcome this problem will have a negative impact on you. So even if you feel reluctant, you must do it. It is a crucial step into manhood and will define you.

Now, you might want to make it a more pleasurable experience, so you can try different methods of boosting your confidence. What I personally do (not for flirting though, but to feel better) is to inform myself about manhood and to try things that stimulate this transition. I read about the psychology of a man, I try workout routines used by soldiers, I read about different types of beards and trim mine to feel good when I look into the mirror, I try sports, I read about male leaders and get inspired by them, etc. These might help you boost your confidence overall. For flirting particularly, I would just try again and again learning how to adapt to different women and to find the types that would make me feel comfortable with. Just try to be confident and to push yourself into conversations. After a little while you will feel much better about it and very grateful for doing it. We all used to feel the same once. After doing it for a while, I feel much better and I actually enjoy it very much. It makes me feel confident about my masculinity. It also worked with interviews. I was afraid of them, but now, after practicing, I feel like I can't wait another interview just to impress employers with my skills.

After all, you have the skills, and the potential and you are now facing the final stage, applying them to get what you want. So do it and good luck.

Edit: I remember reading in a book (King, Warrior, Magician, Lover) about some ancient tribes who used to do a ritual for boys who started having sexual desires for girls. The chief used to observe a boy's interest in girls and say "The boy must die!". Older members beat him and leave him for a night in the forest to be "eaten alive" by insects, and then return for him the next day. Then they said "The boy died! The mas was born!". Indeed it is unsafe and risky, but the point is that your problem is as old as humans are, and people found out that giving a strong shock to boys at that stage helps them with such problems. What we learn from this is that it can be a difficult experience and we have to face it as part of our transition process.