History or Zoology?

Hi,

I am a first year at the Uni of Glasgow, studying Joint Honours History and Politics. The first term was pretty , as I found out that Politics course was not what I expected it to be. History was also unbearable as we did Scottish medieval history and I find medieval history hopelessly boring. I had Business and Management as my third subject, not meeting my expectations as well. This term I chose Central and Eastern European Studies as a alternative to Politics course, and am doing Asian Religions as the third subject. Both are great and I also like this term´s History course. However, I am still dubious if I made the right decision about my Uni studies. I was firmly determined to study Veterinary throughout my childhood and much of my teen years. The only obstacle was my inability to learn and understand Chemistry. I fell in love with History during the last four years of high school (I am from Slovakia). Now I consider taking up Zoology or Marine & Freshwater Biology. However, I don't know if I could just transfer to lets say Zoology (1st year) without submitting a sbrand new application to UCAS? And even if I could I don't know if I would cause I am just so afraid and insecure about what I really want to study and do. I know I am still young and can change my choices but still the uncertainty of my future gives me sleepless nights.