If I did not make the request, I would not have received the promotion and increase as quickly as I did. Instead, my employer would have given me an eventual promotion and smaller increases, years later. I never assume that I will receive what I deserve. After all, the worst thing they can say is no. If they had told me this I would have asked what specific areas and skills I lacked to get to the next level.
Confidence goes a long way.
If you are lacking confidence, then others may also lack confidence in you. Seek other employment opportunities . Sometimes you must find other opportunities outside your existing firm, especially if your employer is a very small organization without room for advancement. There may be opposition in large firms, because of politics or other restrictions. Only you can determine the right opportunity for yourself.