"I apply for the same position I have now at different companys, because I know they pay more. What I make now, is entry level since this is my first job using my degree.
Currently I say, because work is slow and want to grow. But what I really mean is, because I want more money."
Your answer needs a little work. Most of us are motivated by money, and we all know that. But you have to believe in the mission of the company you are working for - even if you have to try a little to believe that.
When asked that question, you want to focus on the opportunity and the company you are talking to. When I hear "work is slow and want to grow", what I think is "you don't work hard enough, or find things to make yourself productive, and want to get paid to keep doing that."
It's not your potential employers problem whether or not you are happy at your current job. However, they do want to hire people that care about the work they do. Try and find something you care about, and bring that enthusiasm into your interview.
Q "why are you wanting to leave your current position/job?"
A "I am intrigued by the work you do, and the direction the leadership is taking this company. My skills and experience will help Your Company continue to move forward - and I know I will do great work in the environment you have created here."