You will never feel confident about your programming skills.
The way you describe your skills, points to a mindset where you will be never satisfied with your skills. You mastered C++? Wait there is Java! You mastered Java? Wait there is Parallel Programming. You mastered Parallel Programming in C++ and Java? Wait there is SOA! There is OOD! And MVC! SOLID! Functional Programming! Web Programming! Cloud Programming! Mobile Programming!
The point is not to feel depressed because of this. You need to push some buttons in your head: Your doubt about your skills is pure fuel. You will likely never reach some satisfying level of programming skills. As long this is the case, you will move forward. The hard part is to realize it and do something against it, although there will be never a goal. The longer you can bear it the higher your skill level will be.