So I know HTML, CSS and how to create a backend(I am a developer). I can play around in photoshop. But I guess I lack something to create a real stunning layout. I end up using something like bootstrap or some template but I feel guilty doing that. How do you learn to create nice original layouts? Is it a talent like music?
You need creativity, also you need to have seen a lot of well-designed websites and take note of all the happens there. Try smoking some green if it's legal where you are, as a matter of fact it may actually boost your creativity.
So many years in the industry and I still can't design as well as the full fledged designers... I guess I just don't have as much creativity juice, nor have I smoked any greens before. But learning the basic design principles and studying the sites at Awwwards is a good place to start.
You are a developer, That's fine don't be too hard on yourself for using a third party design most developer do. To build a responsive layout like you mentioned you need to spice up your CSS skills a bit with some new features provided in CSS3, Responsive and mobile friendly layout are easy to design. Take a god look at the Simple Responsive layout I attached to this post and see what you can learn from it.