Are there problems from mixing different sources of teachings?

I discovered Buddhism by reading and practising the Theravada teachings. As I wanted to make some progress, I started looking for a teacher who could guide me and direct my practicing. So I decided to go to a local Mahayana School near my home, and I've been going there for two years now. Until this time I've still been practicing both Theravada teachings and Mahayana. Also I discovered about the S.N. Goenka Vipassana movement and did some courses (retreats). I would like to know if is there a problem from mixing different sources of teachings in my practice? I saw many famous teachers who searched different teachings, till finding their way to enlightenment. Is it inappropriate mixing different sources of teachings, and could it disturb/confuse my practice? I would appreciate seeing different perspectives, and their own experiences from other practitioners. Thanks :)