Changing my major

I am a college freshmen and I am currently majoring in biology with an emphasis on premed. I knew I wanted to do something with medicine during my third year when my grandfather got sick of a terminal illness. The more thoughts I had about it the more interest I had in this major. At first I was like what do I really want to become. I took deep thought of it and decided I wanted to become a surgeon. Knowing that pre medicine was going to be hard I decided to do it. However now I am in my spring semester questioning my choice since last semester I got a F on my biology class. Now I am retaking it and current have a B- and I have a C on microbiology. If I am doing so bad in these class should I even keep going for my dreams or change it? Need some advice.