honestly I was the same, chemistry GCSE I did the best in and got an A*, but when it came to A levels I found it so much trickier and biology was the subject that I found came the most naturally to me. I started off with C’s in chemistry A level but I managed to get an A* in the end, honestly it just takes a lot of revision, making sure you do really thorough notes before each topic test and be sure that you understand something before moving on, because as you go along the course a lot of the early knowledge gets built on