Science subjects can sometimes appear a little daunting and difficult. This is partly because of what people may say about the subjects, the positive attitude of the student, how encouraging the teacher is etc.
I can however assure you that if you just apply yourself and avoid letting the attitude towards science subjects override your desire to learn you will see a change. Also get a friend or two who are really good at science and they can explain the subjects to you in a simple language that you can understand.
Finally ask questions. Ask when you are unsure, ask when you want to clarify something, ask even just to show off that you have understood!!!
You could try find out what specifically you dont like about science subjects e.g. moles concept and probably find a teacher or a student who can help you understand some of the hard stuff. Not all people like science but it would be good if you tried your best so as to pass your national exams and after that you will have a much broader range of courses to choose from for your university studies