I'm sorry to hear that. The first thing you can try is to watch the many good online tutorials on Youtube. The reason why you fail may be due to the style of teaching of your professor doesn't really suit you. Second, I suggest doing exercises at the end of each chapter for the math textbook and make sure you really understand the logic (and ask your professor if not). Building interest in math is very important in learning math. I know it will be tough at first but if you are passionate in engineering, I feel confident that you can overcome the hurdle